I agree the best thing at Discovery Cove is snorkeling with the rays. I have no idea how the new fresh water oasis is, but can't wait until we go back next year. We paid for the photo package, and my absolutely favorite picture of my son ever was taken by a DC photographer. The dolphin swim was fun, and the aviary is great.
We all really liked Allure, the Call of the Ocean show at Sea World. But I don't think there was a single show we didn't like, except Shamu Rocks, as it was too loud for all of us. To get decent seats, you need to get to each show about 30-45 minutes early, depending on the crowds. I second the idea of getting to the Clyde & Seamore show early. That mime is hilarious.