When you arrive at Ko Tao, they will already on the boat to Ko Tao try to convince you to book your diving course with them. If you already find out which diving school you want to join for your course, don't change. The most of the diving schools offer a price of 8500B You think that is cheap, it is only 500B cheaper then all the other diving schools. The cheaper ones have big groups (up to 8), big and slow boats who drop you off at the diving site, you get class while you're on the way. It is so much better to pay 500B extra for small classes.