No idea what the diving is like but it appears that at least in Phuket
some of the damage (although still horrific) is being over stated.  We
dived with these guys a month ago - they were right behind Kata beach so
you would expect major damage.

http://www.scubaboard.com/t82583-phuket_thailand_-_tsunami_update_from_a_local.html

I also heard earlier rumours the laguna beach hotel had been pretty much
destroyed - apparently however they currently only have about 10 rooms
out.  Sheraton even less and Banyan Tree/Allamanda guests didn't notice
anything.  Even Dusit only has about 30 of it's beach front rooms
unusable.  Patong looks a complete mess as does Kata Yai and Phi Phi Don
appears devastated but for Phuket even Patong which looks the worst hit
is pretty much immediately up a hill once you are over the beach road so
it will be limited.

Living in SE Asia I have been amazed by the resilience of people here.
The Balinese after the bomb showed great fortitude and I fully believe
the Phuket residents will be the same - I certainly hope so.  I for one
will be going as soon as possible.  The tourism trade makes up
apparently 10% of Thai GDP, they need our support in this area as well
as immediate aid or their national disaster is going to get much worse
in the long run.  I have seen some local sites here where all LOBs are
still going ahead.  I hope people show up.

Sri Lanka and others looks a different story - the damage looks far
worse.  I think the media coverage is less due to the lower
international interest as the east side is not really a tourist
destination, at least not to the same degree.