Koh Tao is mainly for people who are going diving. The guesthouses offer discounts for divers or sometimes won't even let nondivers stay there. Helen was thinking about doing a dive & Charlie & I wanted to. However, in the end, we thought we would dive after Helen had left us so that she had more beach time for her holiday.
The beaches here were nothing special, however we did take a taxi boat to an amazing spot where the snorkelling was really good. There were loads of tropical fish that stayed really shallow & the water was so clear you didn't even need to stick your head underwater to see them.
We decided to spend the rest of Helens holiday in Koh Samui, where we heard that the beaches were really nice & the nightlife was good too.