As stated above, the dolphins are swimming around in the tank, and people are waiting, 2-3 people deep, to get a chance to touch a dolphin. It gets pretty crazy, as the dolphins are most focused on the people that have food for them. They do cue in on the trainers there though, so if you can get a trainer's attention he or she might be able to help you out.
I thought it a rather miserable experience, actually - the dolphins are brought down to the level of begging for food, and not everyone trying to touch the dolphins is being nice about it. I'd actually love to have Seaworld closed, and the animals moved to a more natural habitat, instead of inland Florida.