UFOrb
Contributor
agree, shop very carefully when choosing dive ops in Phuket. Or better yet, go to Koh Tao, Koh Samui or Koh P'nang. Much better diving and better dive shops.
I agree about choosing carefully but I disagree about better diving in the gulf of Thailand. Koh Tao has some decent enough sites but forget about basing yourself in Koh Samui or phangan if you're on a diving holiday.
In general, Andaman coast offers the best diving in Thailand. If you want to avoid Phuket try phi phi, Lipe, or better still Koh Lanta. Or do a liveaboard.
I realise this is totally off topic though!