Not to change the subject since the collecting practices of reef fish is something that would make an excellent thread on its own, but I'd like to comment on dive sites...
Australia was mentioned a few posts ago, and I'd like to second the fact that this was an incredible experience for me. Back in '99 I spend a few days (although I could have spend the entire trip here!) on Heron Island, located on the Great Barrier Reef near the southern-most point of the actual marine park. The diving was incredible!
In fact, the entire island was incredible! You get there either by helicoptor or catamaran from Gladstone. When we were there, it was $300 AU/night, but it's all-inclusive except for alcohol. The dive boats were never overcrowded and always inexpensive, and we saw tons of marine life: nurse sharks, blacktip reef sharks, a huuuuuge manta ray, butterflies, anemones, sea turtles, etc...
Depending on the time of year you go, you can also witness sea turtles nesting/hatching (without lights of course!), whales migrating just off-shore, and I forget what else. It's a very natural setting, and you can learn a lot by joining in on reef walks, snorkeling from shore, fishing - the boat takes you just outside the actual park, so you can legally catch dinner. I caught quite a few different species including something called a rock fish, I believe. That must have been the ugliest thing I've ever seen! I did catch a coral trout that I took back to the island and had prepared for us for dinner that night. That was yummy!!
Some day when I take my husband to Australia, I will definitely look into going back to Heron Island.