If there is one thing Koh Tao is famous for, it is for its diving conditions. Even though there are thousands of people getting their diving license there every year, the underwater scene is absolutely stunning.
I booked my PADI Open Water course with Crystal Dive, and got my accommodation for five days, two free barbecue buffets, one free t-shirt and got free rent of books and equipment included in the course package. Koh Tao is also known for being one of the cheapest places in the world to do the Open Water course.
The price is also not the only reason why Koh Tao is a good place to take the diving license, but because of the fact that everything and everyone on the island are there because of the diving possibilities. People come from all over the world to work as instructors, or just to make their hobby into a fulltime lifestyle.
For those who are not interested in scuba diving, there are also some quality beaches, and good restaurants that would work for a quiet vacation, but I would mainly recommend the place for people who are interested in seeing the underwater wildlife, either fully equipped with scuba gear or just with a snorkel and a mask.