I have done just about every tour in WDW, and this was by far the best one that I have done. Its a bit pricy but I felt it was worth every penny.
It lasts for about 2 hours and you should arrive about 30 minutes early by guest relations before you enter Epcot. You are then taken backstage and enter a ear entrance of The Seas with Nemo and Friends. You start off by getting changed into a wet suit (a wet not a dry suit so wear a bathing suit). You then proceed to go on a tour of the backstage of the Seas, this part of the tour is quite educational but very interesting. You are then taken to see where the dolphins are cared for and kept at night.
The next part of the tour is the best because you are brought into the actual tank that houses the living seas. If you cant swim it might not be a big deal because you are standing on a ledge and only go waste deep. The dolphins then perform a series of tricks and you are given an brief anatomy lesson. You then each get a turn to pet and take a picture with the dolhpin. This is the end of the tour and it lasts about 2 hours. At the end we were given an exclusive shirt, pin, and we each got a picture.
This was a great experience and I highly recomend it.