I agree the interaction with the people watching the tank was indeed fun...and the behind-the-scenes tour was impressive. I keep a small marine aquarium in my dental office (yep, I have a Nemo), so I have a good idea of how much work it is to keep such a habitat so clean and well functioning. It's a chance to see the dolphins and manatees up close as well.
I called WDW directly (1-407-939-8687) to book the tour, the cost was $175 pp, and we were in the water for a solid hour. There were 3 time slots: 4:30, 5:30 and 6:30 pm. My personal conclusion to the time choices was that the Coral Reef restaurant is busiest during those hours and the tank is the dining room's main attraction. I can't help smiling at the irony of eating seafood in a tankside restaurant!
When I called WDW, they told me that they were only booking this tour within a 90 day window. Since I wanted to do it the day after Christmas, I made sure I called ON the first available date. At that time there was plenty of availability, and at dive time, there were 18 divers in the tank on the tour. With 4 dive-masters and a professional videographer in the water with us, it still never felt crowded. The camera man did a very professional job of making a 20 minute DVD of our dive. Each diver gets a good amount of face time with the camera, and if you have friends/family dining in the Coral Reef at the time you're in the water, the photographer makes sure to get a shot of you in front of the window with them in the background...it's extremely well done, and a unique souvenir, well worth the additional $35. It's produced and ready for you as you are ending your tour, they take cash and credit/debit cards.
I have since googled aquarium diving, and found there are more places to do it than I'd thought...more things to add to the bucket list!
We've taken family to this a number of times. And we agree that the most "fun" part of the dive is the people on the OTHER side of the glass.
Meanwhile, if memory serves, FL residents get a discount. ????