I love the Living Seas pavillion at Epcot. I think it is one of the world's largest tanks- they have dolphins, stingrays, manatees, some sharks, etc. You could spend a few hours in there if you want to look at all the different displays. The new Turtle Talk w/crush show is really cute, too. -Steph
As as endangered species, Disney does not actually own any Manatees. The only ones ever at the Living Seas are injured or sick and are being rehabilitated. Sometimes they will have a few, sometimes they won't have any. They are a great facility for Manatee rehabilitation.
The same two manatees were there in May and December of this year- I'm pretty sure they were the same, one of them has a badly damaged tail. They are really cute though!