I completed my Advanced Open Water Diver here and ...

I completed my Advanced Open Water Diver here and did several fun dives. Very competent and nice instructors (Thanks, Oli!) And Dive Master. There is a lot of emphasis on safety and the equipment was in good condition. Although Crystal is a large diving school (and the boats are sometimes very crowded), the individual groups were never too big.

The diving course included two nights in the Thai-style bungalow. This is definitely a good deal for backpackers on a budget. If you want a higher standard or spend more, I would recommend another place to stay.

What can be improved: When I was on Koh Tao, Crystal unfortunately had problems with credit card payments and Paypal. I therefore recommend to bring the amount for the course in cash.
Likewise, I could not choose underwater photography as a specialty because I did not have my own camera. Here a reference to the homepage would have been good, or the possibility to rent a camera (possibly for a fee).