Discovery Cove is an amazing adventure. It is really the type of thing that you do only once for the experience, since it is so expensive, but it was well worth the cost.
Highlights of Discovery Cove include feeding the birds in the aviary (watch out though, my husband got bit by one!); snorkeling; swimming in the tropical lagoon/lazy river which has pretty waterfalls; lounging on the gorgeous white sand "beach"; and of course the main attraction, swimming with a dolphin!
Discovery Cove is all-inclusive, and you have continental breakfast, a big delicious restaurant lunch with dessert, and unlimited snacks and drinks all day. There is also no additional fee for the use of wetsuits, and they provide disposable snorkeling masks and goggles. Lockers are also free to use for the day.
I would recommend Discovery Cove to anyone who is a good swimmer. They have life vests, but the water is very, very deep which can be scary if you can't swim. Some areas were 15-plus feet deep!
The dolphin swim is 30 minutes long; you pet the dolphins, kiss them, watch them do tricks, and ride along with them as you hold onto its fin and it pulls you along. They have photographers who take your photos and you may purchase them afterwards.
The snorkeling was also incredible, there are tons of fish, rays, and you can even see barracudas and sharks (those are behind glass, but the regular fish aren't!).