i'm a guessing the format is similar to the Aqua Seas Tour that I took last year. The 3 hour tour includes a tour of The Living Seas pavilion including some of the back stage area where they do research on various sealife including the dolphins, and a little video presentation about TLS's environmental mission. It also gives you time to change into and out of a wet suit, and time to get everyone a little familiar with the tank environment and a quick intro to your divemasters and some of the animals you will encounter, etc.
The experience is pretty unique at Disneyworld. This is one of the few ways you can become part of the show on stage. While you dive, you will be on stage for all the other guests to see, wave to, and interact with. Some people even spent their whole 30 mintues playing with their children through the glass of the observation deck. If you are interested, I would highly recommend Dive Quest, or the Aqua Seas Tour if you are not scuba certified.