This is coming from a newbie!
I really enjoyed the dive in a hugh fish tank(GA Aquarium).It was like luxuary diving. They had all the gear set up pool side for you. They had a locker with your name, wet suit/boot size and towels already in them for you. You are guaranteed to see whale sharks, manta ray, hammer heads, and ton's of other fish. The whale sharks seemed to stay closer to the surface when I was there. So I spent a lot of time looking up at them.
The manta ray and hammer head were very curious about the divers. They came gliding by within a foot of me. It was like they were playing a game of chicken with me on there home turf.
The Aquarium also has swim/snorkel with the gentle giants too. It seemed to be a better way to see the whale sharks since they stay near the surface. Plus it seemed the swim had a little pony bottle with reg, so you could put you face underwater without using a snorkel but it did have a snorkel vest to keep you from diving under the water. Might be the best way to see the whale sharks?
There is alot more to my trip but I start rambling to much!
The previous threads link is much more descriptive than my post.
I think its is cool, I can say I have been there done that once, but probably will not do it again, because of cost.
Safe diving
Tony