You might be right. I just found this... Aquatours sounds like what you are referring to. I wonder if it is still being offered...
Special Guest Experiences at the Living Seas Benefit the
Disney Wildlife Conservation Fund!
Disney's Dolphins in Depth
This three-hour program is an in-depth, behind-the-scenes experience to learn more about the dolphins and research at the Living Seas, as well as to increase awareness and appreciation for their counterparts in the wild. This program educates Guests and provides valuable information to create a better understanding and heighten appreciation for these marvelous creatures.
Dive Quest
The ultimate dive is in a 6-million-gallon indoor aquarium with more then 65 species of marine life, including sharks, turtles, eagle rays, and diverse tropical fish. This dive offers guaranteed calm seas, no current, unlimited visibility, incredible marine life, and bright coral structures. It could only happen at the Living Seas in EPCOT!
Aquatours
This unique program offers an up-close look into more then 65 diverse species of marine life, including sharks, turtles, rays, and tropical fish. This adventure takes Guests into the water to explore the Living Seas marine environment using a Scuba-Assisted Snorkel (SAS) unit. Before entering the water, participants tour the aquarium and learn about some of the marine life they will encounter on this amazing aqua tour adventure.