My review is for diving in Kohn Phi Phi.

The island is full of dive operations. Great choice prices are the same so pick one you like.
Unfortunately I was there during rainy season and boat rides were rough but once under water it is one of the prettiest places to dive. Visibility was not as good as during the winter time, so I was told but otherwise a really good experience.

The nice thing about Phi Phi is that once you are done diving seafood and beers are waiting on every corner