Research and Develop underwater scooters for diving

Ngôn ngữ trình bày: Bản báo cáo: Tiếng Anh  Tiếng Việt  Trình bày bảo vệ: Tiếng Anh  Tiếng Việt  TRƯỞNG BỘ MÔN GIẢNG VIÊN HƯỚNG DẪN Ký, ghi rõ họ tên Ký, ghi rõ họ tên  Được phé

MINISTRY OF EDUCATION AND TRAINING

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY FOR HIGH QUALITY TRAINING

GRADUATION THESIS ELECTRONICS AND TELECOMMUNICATION

ENGINEERING TECHNOLOGY

Ho Chi Minh City, July 2023

RESEARCH AND DEVELOP UNDERWATER

SCOOTERS FOR DIVING

ADVISOR : NGUYEN VU LAN STUDENTS: LE HOANG HOA TRAN QUOC TOAN

NGUYEN MINH HUY

SKL 0 1 0 8 4 6

MINISTRY OF EDUCATION AND TRAINING

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY OF MECHANICAL ENGINEERING

GRADUATION THESIS

Ho Chi Minh City, July 2023

RESEARCH AND DEVELOP UNDERWATER SCOOTERS FOR DIVING

Advisor: NGUYEN VU LAN, Ph.D

Students: LE HOANG HOA – 19146122 – 19146CLA1

Course: 2019 – 2023

TRƯỜNG ĐẠI HỌC SƯ PHẠM KỸ THUẬT TP HCM CỘNG HOÀ XÃ HỘI CHỦ NGHĨA VIỆT NAM

Độc lập - Tự do – Hạnh phúc

KHOA CƠ KHÍ CHẾ TẠO MÁY

NHIỆM VỤ ĐỒ ÁN TỐT NGHIỆP

Giảng viên hướng dẫn: TS Nguyễn Vũ Lân

1 Đề tài tốt nghiệp:

- Mã số đề tài: 22223DT260

- Tên đề tài: Research and develop underwater scooters for diving

2 Các số liệu, tài liệu ban đầu:

Kích thước, kết cấu, hình dạng của thiết kế

Các phương trình động học

Sử dụng DC motor

3 Nội dung chính của đồ án:

Tính toán, thiết kế phần cứng phù hợp, thân thiện với người dùng

Tính toán, lựa chọn động cơ phù hợp

Thiết kế thân thiện với môi trường

Khả năng chống thấm nước và ăn mòn

7 Ngôn ngữ trình bày: Bản báo cáo: Tiếng Anh  Tiếng Việt 

Trình bày bảo vệ: Tiếng Anh  Tiếng Việt 

TRƯỞNG BỘ MÔN GIẢNG VIÊN HƯỚNG DẪN

(Ký, ghi rõ họ tên) (Ký, ghi rõ họ tên)

 Được phép bảo vệ ………

(GVHD ký, ghi rõ họ tên)

DISCLAIMER

Project tile: Research and develop underwater scooters for diving

Advisor: Nguyen Vu Lan, Ph.D

Student name: Le Hoang Hoa Student ID: 19146122 Class: 19146CLA1 Student name: Tran Quoc Toan Student ID: 19146090 Class: 19146CLA2 Student name: Nguyen Minh Huy Student ID: 19146006 Class: 19146CLA2 Graduation thesis submission date:

Disclaimer: “We hereby declare that this graduation thesis is the work of our own research and implementation We do not copy from any published article without citing the source If there is any violation, we take full responsibility.”

Ho Chi Minh City, July 21st, 2023

We would like to sincerely thank Professor Nguyen Vu Lan for his guidance, support, and encouragement throughout this journey, valuable feedback and insightful comments on our work His contributions have been invaluable in shaping the direction and improving the quality of our thesis

We would like to express our appreciation to our families for their unfailing help and support during our school years Their compassion and empathy have served as a constant source of inspiration and drive

Finally, we want to express our gratitude to all of the people who have helped us along the way Their support and suggestions have been crucial in assisting us in achieving this accomplishment

We appreciate your encouragement, and support Without your assistance, we could not have succeeded

ABSTRACT

RESEARCH AND DEVELOP UNDERWATER SCOOTERS FOR DIVING

This Mechatronics engineering thesis focuses on the development of an underwater scooter, a device that allows individuals to move efficiently underwater The project aims to design and implement a mechatronic system that incorporates propulsion, control, and safety features for the underwater scooter The system includes a direct current motor, a propeller, a battery, and a control mechanism that allows for smooth movement and maneuvering underwater The design process involves the use of computer-aided design software and simulation tools to optimize performance and ensure proper functionality of the system

In this project, we used 3D printed plastic materials for the underwater scooter The 3D printed plastic materials are expected to provide the necessary strength and durability required for the underwater scooter to operate effectively Additionally, the design includes a waterproof seal to prevent water from entering the electronic components of the scooter, ensuring its safe and reliable operation

The final product is expected to offer a waterproof design, ensuring safety and an enjoyable experience for users while promoting environmental sustainability and conservation

TABLE OF CONTENTS

GRADUATION PROJECT TASK i

DISCLAIMER ii

ACKNOWLEDGEMENTS iii

ABSTRACT iv

TABLE OF CONTENTS v

LIST OF TABLES ix

LIST OF FIGURES, DIAGRAMS x

LIST OF ACRONYMS xiii

LIST OF SYMBOLS AND PARAMETERS xv

CHAPTER 1: INTRODUCTION 1

1.1 Motivation for the research 1

1.2 Scientific and practical significance of the topic 3

1.3 Target 3

1.4 Subject and scope of the research 3

1.4.1 Research subject 3

1.4.2 Research scope 4

1.5 Research method 4

1.6 Graduation project structure 4

CHAPTER 2: TOPIC RESEARCH OVERVIEW 6

2.1 The marine environment 6

2.2 Diversity of marine ecosystems in Vietnam 7

2.2.1 Vietnam marine ecosystem 7

2.2.2 Diversity of marine ecosystems 7

2.2.3 The economic potential 8

2.2.4 Dive sites in Vietnam 8

2.2.5 Types of beach tourism activities 10

2.3 Underwater leisure activities 11

2.3.1 SCUBA diving 11

2.3.2 Snorkeling 12

2.3.3 Freediving 12

2.3.4 Sea walker 13

2.4 Underwater navigation 13

2.5 Diving strength 14

2.6 Underwater scooter - the new generation of diving 15

2.6.1 Underwater scooter definition 15

2.6.2 Underwater scooter device 16

2.6.3 Potential of underwater scooter 17

CHAPTER 3: LITERATURE REVIEW 18

3.1 Body surface area 18

3.2 Drag coefficient 18

3.3 Propeller design 22

3.3.1 Propeller anatomy 22

3.3.2 Propeller parameters 22

3.4 Buoyancy 25

3.5 Power and consumption time 25

CHAPTER 4: REQUIREMENTS AND SOLUTIONS 26

4.1 Hull material 26

4.2 Hull designs 28

4.3 Electricity supply 29

4.4 Display screen 30

4.5 Microcontroller 30

4.6 Depth measurement 30

4.7 Waterproof method 31

4.8 Propeller design 31

4.8.1 About Caeses® 32

4.8.2 Applications 32

4.8.3 Popularity of CAESES® in the field 32

4.8.4 How to use CAESES® to design B-Series propeller 32

CHAPTER 5: DESIGN AND IMPLEMENTATION 35

5.1 Block diagram 35

5.1.1 Block listing 35

5.1.2 Block diagram 35

5.1.3 Operational description 35

5.2 Mechanical design 36

5.2.1 Calculation and equipment choosing 36

5.2.2 Drafting 45

5.2.3 Hull design 45

5.3 Electrical design 52

5.3.1 Electrical block 52

5.3.2 Calculation and design 52

5.3.3 PCB design 54

5.4 Control design 54

5.4.1 Overall flow 54

5.4.2 Check GPIO change loop 55

5.4.3 Measure sensor value loop 56

5.4.4 Slowly change PWM value 57

5.5 Design results 58

CHAPTER 6: EXPERIMENTS AND DESIGN ANALYSIS 61

6.1 Establish target specifications 61

6.1.1 Qualitative statements 61

6.1.2 List of metrics 61

6.1.3 Correlation matrix 62

6.1.4 Proposed specifications and experimental methods 63

6.2 Operation experiments 63

6.2.1 Static tests 63

6.2.2 Dynamic tests 64

6.3 Analysis 70

6.3.1 First test 70

6.3.2 Second test 71

6.3.3 Final test 71

6.4 Final specifications 71

CHAPTER 7: CONCLUSION AND RECOMMENDATIONS 73

7.1 Conclusion 73

7.2 Recommendations 73

REFERENCES 74

APPENDIX 1: B-SERIES B.4.40 TAYLOR B P -δ DIAGRAM 76

LIST OF TABLES

Table 3.1 Drag coefficient of simple 3D and 2D shapes 19

Table 4.1 Carbon Fiber-Reinforced Thermoplastic Composites comparison table 26

Table 4.2 Comparison table of underwater scooter models on the market 28

Table 4.3 Electricity supply comparison table 29

Table 5.1 Motor and propeller calculation based on Taylor 𝐵𝑝 − 𝛿 chart 37

Table 5.2 DC motor ZOGO 68S-RA/CW 38

Table 5.3 Propeller parameter table 39

Table 5.4 Battery parameter table 43

Table 5.5 Power consumption table 43

Table 5.6 PVC pipes parameter table 44

Table 6.1 List of needs 61

Table 6.2 List of metrics 61

Table 6.3 Correlation matrix 62

Table 6.4 Proposed specifications and experimental method 63

Table 6.5 Device size measurement table 63

Table 6.6 Screen response time test 64

Table 6.7 Speed 1 change response time table 65

Table 6.8 Speed 2 change response time table 65

Table 6.9 Speed 3 change response time table 65

Table 6.10 Ampere test 66

Table 6.11 Scooter head waterproof test 66

Table 6.12 Scooter handle waterproof test 67

Table 6.13 Scooter screen waterproof test 67

Table 6.14 Scooter body waterproof test 67

Table 6.15 Scooter body waterproof test 68

Table 6.16 Scooter switch waterproof test 68

Table 6.17 Scooter overall waterproof test 68

Table 6.18 Speed test in 3 levels 69

Table 6.19 Assembly time tests 70

Table 6.20 Final specifications 71

Table 6.21 Comparing with available products on market 72

LIST OF FIGURES, DIAGRAMS

Figure 1.1 Swimming activity 1

Figure 1.2 Water-related activities and sports 2

Figure 1.3 Underwater with Diver Propulsion Vehicles 2

Figure 2.1 Marine ecosystems help attract tourism 6

Figure 2.2 Sea tourism activities in Con Dao 7

Figure 2.3 Vinh Ha Long 8

Figure 2.4 Nha Trang bay 9

Figure 2.5 Snorkeling in Vinh Hy 9

Figure 2.6 Phu Quoc island 10

Figure 2.7 Beach tourism in Vietnam 10

Figure 2.8 SCUBA diving in Phu Quoc 11

Figure 2.9 Basic SCUBA diving equipment 11

Figure 2.10 Snorkeling in Nha Trang 12

Figure 2.11 Freediving 12

Figure 2.12 Sea walker activity in Phu Quoc 13

Figure 2.13 Diving with underwater navigation device 13

Figure 2.14 Surface marker buoy 14

Figure 2.15 Underwater exploration 15

Figure 2.16 SCUBAJET PRO Underwater Kit 40071 16

Figure 2.17 Sublue White Shark Mix Underwater Scooter 17

Figure 2.18 Yamaha Seascooter RDS300 17

Figure 3.1 Drag force affects on swimmer body 18

Figure 3.2 Human body position can affect drag force 20

Figure 3.3 Human body in various positions 20

Figure 3.4 Description of drag force experiment in the article 21

Figure 3.5 Propeller anatomy 22

Figure 3.6 Submerged part parameters of ships 22

Figure 3.7 Potential flow and boundary layer growth affect wake velocity 23

Figure 3.8 Propeller pitch 23

Figure 3.9 Taylor Bp-δ chart explanation example 24

Figure 4.1 a) Polycarbonate and b) Polypropylene 26

Figure 4.2 ABS string 27

Figure 4.3 Cup made by PLA material 27

Figure 4.4 PVC material 27

Figure 4.5 a) Yamaha seascooter and b) Sublue underwater scooter 28

Figure 4.6 Buller-shape underwater scooter 29

Figure 4.7 a) Lithium-ion battery and b) Nickel-metal hydride battery 29

Figure 4.8 TFT screen 30

Figure 4.9 Arduino Nano V3.0 ATmega328P 30

Figure 4.10 BMP180 sensor 31

Figure 4.11 O-ring 31

Figure 4.12 Silicon tube 31

Figure 4.13 CAESES® applications on many aerodynamic bodies 32

Figure 4.14 Popularity of CAESES® in the field 32

Figure 4.15 CAESES® B-series propeller design website 33

Figure 4.16 CAESES® B-series propeller result after input data 33

Figure 4.17 3D CAD model generate by CAESES® website 34

Figure 5.1 Block diagram of the device 35

Figure 5.2 Motor ZOGO 68S-RA/CW 39

Figure 5.3 Propeller B-series 39

Figure 5.4 Fluid domain in flow simulation 40

Figure 5.5 Flow simulation with inlet flow velocity 0m/s and outlet flow velocity 1.2m/s 41

Figure 5.6 Cut plots for the velocity distribution on propeller 41

Figure 5.7 Velocity distribution on the propeller 42

Figure 5.8 Underwater buoyancy force description 42

Figure 5.9 Rocket ES7.5-12 43

Figure 5.10 PVC pipes 44

Figure 5.11 Drafting design 45

Figure 5.12 Isometric view 45

Figure 5.13 Exploded view 46

Figure 5.14 System orthographic projection 46

Figure 5.15 Underwater scooter head explode view 47

Figure 5.16 Underwater scooter body explode 47

Figure 5.17 Bottom of battery 48

Figure 5.18 Underwater scooter holding head 48

Figure 5.19 Motor tail 49

Figure 5.20 Motor chamber 49

Figure 5.21 Motor chamber zoom in view 50

Figure 5.22 Mechanical seal of the propeller 50

Figure 5.23 Mechanical seal in assembly with the shaft of the motor 51

Figure 5.24 Mechanical seal position in device 51

Figure 5.25 Scooter cage exploded view 52

Figure 5.26 Electrical block 52

Figure 5.27 Proteus circuit schematic 53

Figure 5.28 MOSFET IRF540N 53

Figure 5.29 PCB wiring 54

Figure 5.30 a) PCB circuit board visualizer and b) PCB circuit board in real life 54

Figure 5.31 Overall flow chart 55

Figure 5.32 Check GPIO change loop flow chart 56

Figure 5.33 Measure sensor value loop flow chart 56

Figure 5.34 Slowly change PWM value flow chart 57

Figure 5.35 Control interface of the device 58

Figure 5.36 Underwater TFT screen display 58

Figure 5.37 TFT screen shows when battery is low 59

Figure 5.38 Underwater scooter LED light at night 59

Figure 5.39 First prototype electrical wiring 59

Figure 5.40 Underwater scooter hull parts 60

Figure 5.41 Underwater scooter head parts 60

Figure 5.42 Underwater scooter body parts 60

Figure 5.43 Underwater scooter tail parts 60

Figure 6.1 Ampere test results in 3 levels 66

Figure 6.2 Speed test using velocity formula 69

Figure 6.3 Assembly time tests 70

Chart 3.1 Drag coefficient according to simulation results with experimental results 20

Graph 3.1 Drag coefficient of cylindrical bodies in Axial flow 19

Graph 3.2 Test results at speeds below 2m/s 21

Graph 0.1 B-series B.4.40 Taylor 𝐵𝑝 − 𝛿 𝑑𝑖𝑎𝑔𝑟𝑎𝑚 76

LIST OF ACRONYMS

ABS : Acrylonitrile Butadiene Styrene

BCD : Buoyancy Control Device

BSA : Body Surface Area

CAD : Computer-Aided Design

DAR : Disc Area Ratio

DC : Direct Current

DPV : Diver Propulsion Vehicle

GPIO : General Purpose Input/Output

GPS : Global Positioning System

I2C : Inter-Integrated Circuit

IRF : Instrument Response Function

IUCN : International Union for Conservation of Nature LCD : Liquid Crystal Display

LED : Light-Emitting Diode

MOSFET : Metal-Oxide Semiconductor Field-Effect Transistor MWR : Mean Width Ratio

PCB : Printed Circuit Board

PLA : Polylactide

PVC : Polyvinyl Chloride

PWM : Pulse Width Modulation

RPM : Revolutions Per Minute

SCUBA : Self-Contained Underwater Breathing Apparatus SPI : Serial Peripheral Interface

TFT : Thin Film Transistor

UART : Universal Asynchronous Receiver-Transmitter VND : Vietnamese Dong

VOM : Volt-Ohm-Milliammeter

LIST OF SYMBOLS AND PARAMETERS

Description Symbol Unit

CHAPTER 1: INTRODUCTION

For centuries, people have enjoyed swimming, a well-liked water-based activity Swimming is a refreshing and energizing activity that people of all ages can enjoy, whether

it is for fun, exercise, or competition There are countless places to practice swimming, including indoor and outdoor pools as well as natural bodies of water like lakes and oceans The swimming experience can now be improved even further thanks to technological developments like waterproof fitness trackers and underwater music players Swimming is a favorite pastime for many people all over the world because it's enjoyable and has lots of health advantages

Figure 1.1 Swimming activity

Water-based activities like snorkeling and SCUBA diving give special chances to explore the underwater world To view the underwater environment, snorkelers swim on the surface of the water while breathing through a snorkel In contrast, SCUBA diving entails using a self-contained underwater breathing apparatus (SCUBA) to dive further and remain underwater for longer periods of time These activities offer a chance to learn about various types of ecosystems as well as an opportunity to explore underwater landscapes that are otherwise inaccessible and appreciate the beauty of coral reefs and marine life Snorkeling and SCUBA diving can be a safe and enjoyable way to explore the wonders of the underwater world with the right instruction and gear

Swimming, snorkeling, and SCUBA diving are just a few of the water-related activities and sports that have seen a significant rise in popularity over time While there are many tools and equipment options for surface activities like kayaking and surfing, there haven't been many choices for leisure diving and underwater exploration

CHAPTER 1: INTRODUCTION

Figure 1.2 Water-related activities and sports

SCUBA diving and snorkeling used to be the only options for leisurely diving, both of which require extensive training and equipment But thanks to recent technological developments, there has been an increase in the creation of novel tools and vehicles that make

it possible for people to efficiently and easily explore the underwater world

For example, underwater scooters provide both beginning and experienced divers with

an exciting opportunity to explore the ocean's depths These gadgets push the user through the water using propulsion systems, enabling longer and more comfortable dive times They also allow divers to explore more of the underwater environment because of their increased flexibility and mobility

There is no doubt that as technology develops, more cutting-edge tools and vehicles will be created, enhancing everyone's access to and enjoyment of underwater exploration and recreational diving

Figure 1.3 Underwater with Diver Propulsion Vehicles

CHAPTER 1: INTRODUCTION

With the help of this innovative tool, you can travel underwater in a fun and effective way that broadens your access to places and allows you to travel farther The underwater scooter is an essential piece of gear for anyone who enjoys exploring the underwater world, whether they are professional divers, adventure enthusiasts, or just regular people

The scooter's bullet-shaped design has excellent hydrodynamics and an appealing visual, making it easy to control in the water It is simple to use the device's buttons and controls thanks to the hand grips, which were designed to resemble bike handlebars You can travel for extended periods of time underwater with belief due to the device's long-lasting battery and a screen that clearly shows the time and important device status information

The underwater scooter is the ideal tool to advance your underwater adventures, whether your goals are to explore coral reefs, record breathtaking underwater footage, or simply take a leisurely swim

The development of underwater scooters is a topic of great urgency in the field of engineering as it presents a new way for humans to move faster and more efficiently underwater By designing and implementing a mechatronic system that incorporates propulsion, control, and safety features, engineers can create a device that allows individuals

to explore the underwater world with ease and convenience

The research on the underwater scooter has the following goals:

- Development of an underwater scooter,which can work properly in terms of its hydrodynamics, ease of use, and battery life

- Predicting the underwater scooter's potential applications

- Describe any possible disadvantages or limits of the underwater scooter

- Provide recommendations for future developments and improvements in underwater scooter technology, as well as areas for further research

Through these goals, the study looks to encourage future research and development in the area of underwater exploration while also providing a good understanding of the underwater scooter and its potential applications

1.4.1 Research subject

This project aims to evaluate the hydrodynamics, propulsion system, waterproofness, and control mechanisms of the underwater scooter as well as its functionality and design

CHAPTER 1: INTRODUCTION

The goal is to provide a complete design, demo sample and significance of the underwater scooter's performance and capabilities as well as to spot any potential changes or adjustments that might improve the device's effectiveness and usability

1.4.2 Research scope

The developed underwater scooter should operate effectively underwater and has enough functionality to drive people at a controllable speed and display sensor data on a screen Using eco-friendly materials and affordable spare parts

The process for creating an underwater scooter involves several crucial steps Researching on available products to build up an alternative solution Determine the necessary parameters and choose the shape of the device we think to be the most appropriate for our intended use based on this research

Designing the underwater scooter in detail using CAD 3D design software Numerical simulation and analysis were conducted in order to find the ones that best suit our needs

Manufacturing and testing stages involve finding the proper supplies for materials and parts, looking for the right production method The assembly process takes place in a controlled environment, design specifications and safety standards are always followed

Experiment is necessary, the prototype must be tested in a carefully controlled underwater environment All of the experiment's results will be taken note of, prior to a comparison to the theoretical calculations, in order to evaluate the underwater scooter's functionality, mobility, and safety features

Overall, this methodology combines theoretical and practical approaches to ensure that the underwater scooter is designed, built, and tested to the highest standards of quality and safety

The graduation project consists of 9 parts, of which the specific contents are as follows:

- Chapter 1: Introduction: General introduction to the topic

- Chapter 2: Topic research overview: talk about topics related to the marine tourism industry in Vietnam and the difficulties encountered when experiencing underwater tourism

- Chapter 3: Literature review: formulas affecting gear drag, propeller calculations and more

- Chapter 4: Requirements and solutions: outline the options offered to solve the problem of cost, device size, usage time, performance and features

- References: including 8 books, scientific journals and 6 reference websites

- Appendices: includes taylor 𝐵𝑃− 𝛿 chart for B-serial 4.40 and drawings

CHAPTER 2: TOPIC RESEARCH OVERVIEW

The maritime environment, which has various economic, social, and environmental aspects, is one of the most significant habitats on Earth People may obtain significant resources from the sea, including food, fuel, minerals, and medications Additionally, the sea

is a significant source of revenue through fishing and tourism

Figure 2.1 Marine ecosystems help attract tourism

The Earth's climate differs fundamentally from those of the other planets in the solar system due to its 71% surface covered by water Oceanographers and nations throughout the world have historically classified the planet's ocean into four separate regions: the Pacific, Atlantic, Indian, and Arctic seas Scientists agree that the Earth's oceans and seas are the origin of life Life as we know it now might not survive without the seas and oceans (Seibold and Berger, 1989) [17] As a result, the oceans and seas play a vital role in supporting life on Earth Large volumes of atmospheric carbon dioxide are absorbed by the ocean, reducing the amount of this greenhouse gas in the atmosphere [12] In fact, over 25% of the carbon dioxide emitted into the atmosphere annually is thought to be absorbed by the ocean By absorbing and dissipating heat, the ocean also serves to control global temperatures, preventing excessive temperature swings and reducing the severity of weather-related events like storms, floods, and droughts It may be argued that without this "temperature-conditioning machine" known as the ocean, Earth would be a lifeless planet with nothing but a desert

With its abundance and diversity of animal and plant species, the sea environment is equally valuable from a biological perspective The International Union for Conservation of Nature (IUCN) has estimated that maritime regions across the world are home to some

CHAPTER 2: TOPIC RESEARCH OVERVIEW

228,450 species [14] The cultures and economy of many different countries are influenced

by these animal and plant species, which are valuable not just biologically but also culturally and historically

2.2.1 Vietnam marine ecosystem

With a 3,260 km long coastline and a 1 million km2 exclusive economic zone, Vietnam has a vast supply of marine biological resources There are over 20 typical ecosystem types, over 11,000 resident species, and 6 distinct marine biological diversity regions in the marine waters of Vietnam, including the East Sea, the Southwest Coast, the Continental Shelf Region, the North Central Coast, the Central Coast, and the South-Central Coast [13]

2.2.2 Diversity of marine ecosystems

Vietnamese maritime ecological traits may be seen in their tropical, mixed, less distinctive, and north-south contrasting characteristics Around 11,000 resident species, more than 20 typical ecosystem types, and 6 distinct marine biological diversity zones can be found

in the maritime seas of Vietnam, with Mong Cai - Do Son and Hai Van - Vung Tau having higher levels of biological variety than the other regions There are nine places of extremely productive biological yield, together with sizable fishing grounds, in the continental shelf region in particular About 11,000 marine species are known to exist in Vietnam, including 2,458 economically important fish species, 653 types of seaweed, 657 types of zooplankton,

537 types of phytoplankton, 94 types of mangrove plants, and 225 types of shrimp

The list of marine ecosystems in Vietnam as of January 2005 included 2,458 species,

an increase of 420 species compared to the list published in 1985 (which had 2,038 species), and there have been 7 new marine mammal species found, according to studies on the dynamics of marine resources

Figure 2.2 Sea tourism activities in Con Dao

CHAPTER 2: TOPIC RESEARCH OVERVIEW

2.2.3 The economic potential

From north to south, Vietnam's coastline features 125 exquisite beaches The world's most stunning and alluring beaches have been voted to exist in several locations One of the nations with the most breathtaking bays in the world is Vietnam

Given the growing popularity of beach and island travel among both local and foreign visitors, Vietnam is considered to have significant room for growth in this area Additionally, the recent rapid growth of beach and island tourism has created chances to lessen poverty and enhance the lives of those living in coastal regions in various provinces around the nation

Vietnam is not only well known among local and foreign visitors, but it is also gifted with the famed Ha Long Bay, which has twice been named by UNESCO a World Natural Heritage Site Both occasions occurred in 1994 and 2000, respectively The International Convention for the Protection of Natural and Cultural Heritage of the World's criteria have determined that Ha Long Bay qualifies as a World Natural Heritage Site with high worldwide aesthetic significance [15]

Figure 2.3 Vinh Ha Long

These titles have become a bridge, not only for Ha Long Bay in particular but also for Vietnam's tourism in general, to attract international tourists and develop tourism

2.2.4 Dive sites in Vietnam

Vietnam's tourist business has accounted for roughly 70% of its coastal and island tourism operations due to the country's numerous specific opportunities for coastal tourism, particularly the island system Between 2010 and 2019, the number of tourists visiting coastal regions rose more quickly than the national average, reaching 13.6% annually for foreign visitors With about 34 million foreign tourists and 145.6 million domestic visitors in 2019, tourism generated 508 trillion VND in revenue, or around 67.3% of the nation's overall income [16]

CHAPTER 2: TOPIC RESEARCH OVERVIEW

With many entertainment and leisure destinations that attract not only domestic tourists but also international visitors, Vietnam offers famous landmarks, unique and diverse tourism services stretching along the coast to the tourist archipelagos

One of the most popular dive sites in Vietnam is Nha Trang Bay, situated on the central coast of the country Here, divers can explore the colorful coral reefs and encounter a variety of marine life, such as angelfish, butterflyfish, and seahorses Another famous dive spot is the Hon Mun Marine Protected Area, which is home to some of the most diverse marine ecosystems in Vietnam

south-Figure 2.4 Nha Trang bay

Visit Vinh Hy, one of Vietnam's four most beautiful beaches, for a breathtaking view

of the water Vinh Hy Bay is also renowned for its abundant marine life and clean seas Divers may explore the vivid coral reefs here and come across a wide range of marine life, including turtles, whale sharks, and schools of colorful fish Divers of all skill levels will discover the bay to be a perfect location due to its calm waters and mild currents

Figure 2.5 Snorkeling in Vinh Hy

CHAPTER 2: TOPIC RESEARCH OVERVIEW

Further north, Phu Quoc Island offers some of the best diving opportunities in the country Divers have the opportunity to witness a variety of marine animals, including barracudas, groupers, and vibrant nudibranchs, because this island is protected by a marine reserve

Figure 2.6 Phu Quoc island

2.2.5 Types of beach tourism activities

In Vietnam, beach tourism currently holds a strategic position and is one of the industries contributing to the country's development and integration with other countries, promoting the country's economy with a coastline stretching 3,444 km along with many different islands and bays

Beach tourism in Vietnam provides tourists with a diverse range of activities and experiences The most popular types of beach tourism in Vietnam include:

- Sightseeing tours: You can ride on boats equipped with transparent glass to see the coral reefs right under your feet Or if you prefer to get a closer look, you can choose

to dive under the coral reefs and play with the colorful fish in the clear water village

- Visiting beaches: Moreover, Vietnam is home to a number of stunning beaches with white sand and crystal-clear water that draw tourists Visitors may enjoy the beach and engage in activities like swimming and tanning

- Water sports: If you're an adventure seeker, you may go windsurfing, kayaking, parasailing, or you can even try your hand at wave surfing

Figure 2.7 Beach tourism in Vietnam

CHAPTER 2: TOPIC RESEARCH OVERVIEW

2.3.1 SCUBA diving

A sport or activity in which you swim underwater while wearing a body-mounted breathing device and air tank This activity requires multiple equipment, so you must familiarize yourself with them

Figure 2.8 SCUBA diving in Phu Quoc

People have created a variety of items to make diving more convenient while also extending their dive time, such as SCUBA suits that are used to wrap divers to keep them warm underwater or a diving mask that uses oxygen to breathe underwater longer, or simply

a heavy object that allows divers to sink to the bottom of the sea quickly and easily

Basic SCUBA diving equipment include:

 Buoyancy Control Device (BCD)

CHAPTER 2: TOPIC RESEARCH OVERVIEW

2.3.2 Snorkeling

Snorkeling is a form of SCUBA diving with diving goggles and snorkel Simply put, when you join a Snorkeling diving tour, you are provided with a snorkel, swimming goggles and a life jacket for freediving During the development of Snorkeling diving, visitors will receive basic training on how to use snorkels and swimming goggles to see the corals most conveniently At the same time, you will be moved to shallow or shallow water locations, coral reefs near the shore for diving

It is simpler than SCUBA diving because you only need a few tools and some instruction to go out and have fun SCUBA diving also requires more training and equipment

It is appropriate for everyone of all ages

Figure 2.10 Snorkeling in Nha Trang

2.3.3 Freediving

This activity requires the same gear, skill, and preparation as snorkeling before going underwater But the main difference is that the divers would go deeper on their own; this is riskier and calls for experienced divers who are familiar with any issues that can happen when diving

Figure 2.11 Freediving

CHAPTER 2: TOPIC RESEARCH OVERVIEW

2.3.4 Sea walker

This is a type of sport where the diver wears a diving helmet, similar to a safety helmet, which is supplied with oxygen from the surface The helmet has a transparent glass part that allows the wearer to see the underwater scenery and coral reefs without the need for heavy equipment or cumbersome protective gear, making it easier to observe marine life such as fish swimming around you This type of diving is commonly known as "helmet diving" or "sea walking" and is a popular activity for tourists who want to explore the underwater world but are not comfortable with traditional SCUBA diving

Figure 2.12 Sea walker activity in Phu Quoc

Navigation is crucial in SCUBA diving to determine location and distance Common techniques include using natural landmarks, compass heading, and dive computers These methods help divers navigate with accuracy and confidence

The most used method is to remember what it looks like as you pass through the place

or a recognizable landmark that can direct you in the right direction Unless the diver is swimming the same route repeatedly and is quite familiar with it, this act is extremely risky because of human memory

Figure 2.13 Diving with underwater navigation device

CHAPTER 2: TOPIC RESEARCH OVERVIEW

Although we may have heard a lot about GPS on land, the situation is very different underwater Even with modern technology, mapping the underwater world is more challenging because we currently lack a comprehensive map of it When using GPS underwater, it is more likely to show you where you are than when you are above the water

The dive compass is an essential equipment for divers since it offers essential data about heading and direction when underwater Understanding its parts, such as the needle and bezel, and being able to read them precisely, are essential for using it efficiently You should make a note of your starting location and direction before you dive, check your compass frequently while you're underwater, and bring a backup compass or other navigational aids with you The dive compass can improve your SCUBA diving experience's safety and enjoyment with the right planning and attention to detail

Divers can use a surface marker buoy to signal their location to the surface in a quick and easy way You can quickly signal your location by securing one end of the line to your equipment and inflating the buoy as necessary Before your dive, practice deploying and using the buoy to make sure you can do it quickly and effectively

Figure 2.14 Surface marker buoy

Participating in underwater activities is not just an exhilarating experience, but also an opportunity to explore a completely different world Immersing ourselves in the underwater environment allows us to witness a multitude of marine life, coral formations, and other natural wonders that we would never have the chance to see on land [7]

One of the most unique aspects of underwater activities is the sensation of weightlessness and the freedom to move about in three dimensions It's an incredible feeling

to move gracefully through the water, observing the vibrant colors and movements of the marine life around us

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Figure 2.15 Underwater exploration

However, the underwater environment also presents unique challenges to our bodies For example, as we descend deeper into the water, our lungs must work harder to take in air due to the increased pressure Additionally, our heart rate and other physiological responses may differ from what we experience on land It's important to be aware of these changes and

to take appropriate precautions to ensure our safety

Fortunately, most sites that offer underwater activities for tourists are carefully managed and monitored for safety Professional guides and instructors are always on hand to provide guidance and support, and the maximum depth for these activities is typically around

40 meters This ensures that we can explore the underwater world to our heart's content while minimizing the risks

Overall, participating in underwater activities is an incredible way to experience the beauty and wonder of the underwater world By taking proper precautions and following safety guidelines, we can enjoy these activities with peace of mind and create unforgettable memories that will last a lifetime

2.6.1 Underwater scooter definition

Diver propulsion vehicle (DPV), commonly referred to as an underwater scooter or underwater sea scooter, is a portable device used to move divers through the water The scooter's powered propeller and a pair of handlebars provide the diver control over the vehicle's direction and speed

In the world of water sports and entertainment, underwater scooters are a new product This product is made to be used in certain situations, such as diving, ocean exploration, the

CHAPTER 2: TOPIC RESEARCH OVERVIEW

discovery and exploitation of marine resources, or just for fun and exploration of the underwater environment With its built-in motors and control systems, underwater scooters enable users to move around and securely explore challenging or hazardous waters

2.6.2 Underwater scooter device

Underwater scooters are a popular device for exploring the depths of the ocean They come in a range of styles and prices, from handheld units to larger models designed for longer dives With their ease of use and ability to cover more ground than swimming alone, underwater scooters offer an exciting way to experience the underwater world

2.6.2.1 SCUBAJET PRO

The SCUBAJET Pro is a battery-operated jet propulsion system that was initially developed as a scooter for snorkeling and SCUBA diving but has since been adapted to many other watersports Depending on the performance and power requirements you have, there are three different setups for the SCUBAJET

This device was designed with features like battery life from 2 to 4 hours of use, a top speed is up to 4.5 mph Lightweight and simple to use, but still hydrodynamic and the cost is around 2000$, highly recommended by many divers

Figure 2.16 SCUBAJET PRO Underwater Kit 40071

2.6.2.2 SUBLUE WhiteShark Mix

Due to its incredibly lightness and portability, this particular model of SCUBA equipment is ideal for both kids and adults It is perfect for quick, deeper dives and has a depth rating that is appropriate for recreational diving Additionally, this equipment comes in

a variety of color combinations, giving you the option to match your propulsion style to your personal preferences Whether you're a beginner or an experienced diver, having the right equipment can significantly improve your comfort and enjoyment while exploring the underwater world You can make sure that your diving experience is safe and enjoyable by selecting equipment that is portable, lightweight, and customizable to your preferences

CHAPTER 2: TOPIC RESEARCH OVERVIEW

Figure 2.17 Sublue White Shark Mix Underwater Scooter

2.6.2.3 Yamaha Seascooter RDS300

The RDS range of SCUBA gear offers options for both recreational and advanced divers With the RDS250, divers can conserve air and travel further thanks to the propulsion system This gear is perfect for exploring large, shallow wrecks or circumnavigating coral islands while admiring the surrounding marine life However, it's worth noting that the RDS250 is quite heavy, weighing 21 pounds, and has a length of 24 inches Despite its weight and size, the RDS250 remains a portable option, making it an ideal choice for traveling divers and older kids Whether you're a seasoned diver or just starting, having the right gear can make a significant difference in your diving experience

Figure 2.18 Yamaha Seascooter RDS300

2.6.3 Potential of underwater scooter

Due to its affordable pricing and superior performance, this device has promise This product's pricing is reasonable, especially when compared to other similar items currently on the market The device is also extremely effective, conserving energy and facilitating ocean exploration for consumers

The device is also extremely effective, conserving energy and facilitating ocean exploration for consumers People frequently employ power and energy to travel across water

or underneath when they dive The user experience might occasionally suffer as a result of this and tiredness Users may move more quickly and easily underwater with this device, which improves user experience while saving electricity

CHAPTER 3: LITERATURE REVIEW

Body surface area (BSA) is a measurement of the total surface area of the human body There are several methods for calculating BSA, but one of the most commonly used is the DuBois formula This formula calculates BSA based on a person's height and weight:

𝐵𝑆𝐴 = 0.007184 ∗ 𝑊ℎ0.425∗ 𝐻ℎ0.725 (1) With BSA (𝑚2) is the total surface area, 𝑊ℎ (kg) is the weight of the person, 𝐻ℎ (cm) is the height of the person

Drag force is a type of force that resists motion through a fluid, such as air or water Main type of underwater drag force can be:

- Form resistance: the water resistance is dependent on the object body position

- Friction resistance: resistance caused by contact of an object's surface in water

Figure 3.1 Drag force affects on swimmer body

Drag coefficient is a dimensionless quantity that is used to quantify the amount of drag

in the opposite direction of motion that is generated by an object as it moves through a fluid, such as air or water The drag coefficient is a function of several factors, including the shape

of the object, the velocity of the fluid, and the properties of the fluid itself Drag coefficient

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Table 3.1 Drag coefficient of simple 3D and 2D shapes

- Reynolds Number (𝑅𝑒): is a measure of the ratio of inertia forces to viscous forces

of 1000, the drag coefficient of bullet shape will depend on the length-to-diameter ratio

Graph 3.1 Drag coefficient of cylindrical bodies in Axial flow

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Drag coefficient also affects the human body Based on Mun Hon Koo and Abdulkareem Sh Mahdi Al-Obaidi’s simulation [5], we can estimate the drag coefficient of the human body in various positions

Figure 3.2 Human body position can affect drag force

Figure 3.3 Human body in various positions

Chart 3.1 Drag coefficient according to simulation results with experimental results

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According to another study [8], when the diver is in the position with the least resistance, we have the drag force formula when immersed when velocity reach below 2m/s

as follows:

𝐹𝐷 =𝐶𝐷 ∗𝜌∗𝐴∗𝑣2

Figure 3.4 Description of drag force experiment in the article

Graph 3.2 Test results at speeds below 2m/s

CHAPTER 3: LITERATURE REVIEW

To design a propeller, we need to test, measure, and assume many parameters Here is

a method to determine a few basic parameters for propeller selection

𝐶𝐵 = 𝑉

With L, B, T (m), V (𝑚3) is length, width, height and volume of the submerged part

Figure 3.6 Submerged part parameters of ships

- Wake fraction: Cause by non-vicious nature and boundary layer growth The speed of the water following a moving ship or boat is referred to as wake velocity A wake is a disturbance in the water that results from a boat or ship moving through it