Open Water 20


Are you ready to become a certified scuba diver?

The best way to learn scuba diving is with the RAID Open Water 20 Course at Hydronauts Diving Resort. Koh Tao is surrounded by warm, tropical waters making it the premier location to learn how to scuba dive. 

With over 25 local sites you can discover coral gardens, shipwrecks, underwater pinnacles, and artificial conservation reefs. Scuba diving in the Gulf of Thailand is known for being consistently calm, with clear waters and ideal conditions for a relaxed and scenic experience.

No previous experience is required to participate in the 3.5-day open water diving course. You will learn everything you need to know before exploring the underwater world. 

 11,000 THB


Minimum age for Junior Open Water is 12-14 years and 15 for the Open Water 20 diving course.

Must be able to float in a pool for 10 minutes unassisted.

Must be able to swim 200 meters with no swim aids or be able to swim 300 meters using a mask, fins & snorkel.

Must be medically fit to scuba dive.

Step 1 -
Online Study

Begin your scuba diving course before you arrive with e-learning online! You will access all your RAID scuba diving course training manuals and quizzes using a secure login. Contact us to start your Open Water 20 diving course and e-learning today!

Step 2 -
Theory & Workshops

On arrival, you will meet your instructor to review your pre-completed scuba diving course e-learning. Once completed, your instructor will conduct a few workshops and lectures before teaching you how to assemble your diving equipment.

Step 3 -
Pool Training

Next, your instructor will go through all of the necessary skills to learn as a new diver. Together, you and your instructor will spend some time in the training pool with demonstrations and constructive feedback on your skills as you master them underwater. Throughout the pool session, you will be learning to control your buoyancy as this is the MOST important skill to master. Buoyancy control is how we stay at desired depths and neither float nor sink in the water column. 

Step 4 -
Open Water Dives

The Open Water 20 course consists of four dives in the ocean. The day after your pool training, you will finish all of your academic education and head out to sea. You will take our longtail boat straight from the beach to our dive boat to complete the first two ocean dives. These first two dives have a maximum depth of 12 meters, in which you will be demonstrating a portion of the skills from your confined session.

After the dives, it is time to head back to the resort to relax at our beach bar while you debrief with your instructor and log the dives. The next morning, you will be back out on the dive boat for the third and fourth dives in the open ocean. You will demonstrate your remaining skills and then be certified as an internationally recognized Open Water scuba diver!


Flying after your dives? Be sure to give yourself an 18-hour window after your final dive.

Need a place to stay? We are a beachfront diving resort! We offer rooms from mixed dorms, double bedrooms, family rooms, and bungalows for weekly or monthly rent! You can book a room here

Please keep hydrated. Remember to drink plenty of water before and after your dives.

Bring sunscreen (preferably reef safe) and apply it an hour before entering the sea to protect marine life.

Reserve your space now.
Go From Diver, Not... to HYDRONAUT.

Why Choose Hydronauts?​

RAID Instructors​

Our experienced instructors are hand-picked, highly trained, and passionate about scuba diving. We tailor each course and dive to your unique needs.

Beachfront Diving Resort​

Southwestern-facing property including a dive shop, hotel, training pool, cafe & restaurant, dive boat, and beach bar. We offer diving & accommodation packages for every budget.

Guaranteed Small Groups

We guarantee small groups of no more than four students to an instructor or dive guide so that you get the individual attention you deserve.

State-of-the-Art Equipment

We choose to dive and teach in Backplate & Wing BCD with a Long-hose, Short-hose regulator configuration favored by technical divers.

Dive Anywhere in the World

Upon completion of your RAID scuba diving course, you will be issued with an e-certification card that recognizes you as an internationally certified scuba diver.

Low Carbon Footprint

We make every effort to reduce our footprint and use of paper and plastic. All our course materials are hosted online giving you access for life.


Have other questions? These are some of our most frequently asked questions but if they don't answer what you are looking for then please reach out to us directly.

Absolutely we do. You can check out our rooms as we have many different room types to fit most budgets.

If you find a room you would like to book, you can do so here.

Yes! You will need to head over to RAID’s website and create a profile before beginning your FREe-Learning. From there, you can download any and all courses that interest you and begin learning right away. You can even take the quizzes just not the exams. 


While you are able to read the material and take the quizzes, this does not equal a certification. 

The next logical course is Explorer 30, which is our version of the Advanced Open Water that the other agencies offer. 

You can also take Nitrox or just go for some fun dives to show off your newly acquired skills.  

Of course. After completing any quiz or exam, all missed answers will be shown along with the correct answer. During the course academics session, your instructor will go through these with you and explain the answer in further detail. 

Absolutely! This is a great way to literally test the waters and experience the underwater world first-hand without taking a full course.