My trip report for DC is a few posts down.. robinrs is the last poster.
Check out the Discovery Cove/Sea World forum as well on this board.
I loved it, and it was fantastic. There is snorkeling, lazy river, bird avairy, lunch included (nice lunch at that), free parking, free wet suit rental, white sand beaches, stingray lagoon, coral reef, sunken treasure grotto, and stingray lagoon. Of yes, a dolphin swim as well..
It was wonderfully peaceful, and not crowded. DC does come with a seven day pass to Seaworld. You don't have to use the seven days (we used four), but it is included.