Sea World is awesome. DD9 and I visit frequently (two evenings this past week). I agree with the poster who said get the show times, and plan around them. All of them are great, but fitting them all into one day has always been a challenge when we take guests, due to the schedules, and the locations in the park!
If you have the time - and the extra $$$ ($3/person), riding the Sky Tower is a nice time. It revolves and goes 300 ft up in the air, and you get a great aerial view of the park.
DD and I like to spend time in the Dolphin Nursery (to the right when you enter, right before the Marketplace) - you can view moms and babies.
You can feed dolphins in Key West ($4 for 4 fish - the open the stand frequently, and sell until the fish is gone, and then open again later). In this same area are the "Ray"s - you can feed these as well, or just reach in and feel them as they swim around. Watch out - believe it or not they splash! Our favorite animals to feed are the Sea Lions (near the Penguin Encounter) and the Clyde and Seamore Stadium. They are a hoot to watch when they know you have fish. The bark and make all kinds of noise. Sometimes you will see babies with the mom's.
DD also likes to spend time playing in Happy Harbour. This is near the Shamu Stadium and Wild Artic. Right now it is under construction, but there is a great big "jungle gym" - can't think of the word - for climbing and playing - nets, tunnels, slides, etc.
Another good tip was given when they said go to Wild Artic during Shamu, or at an off time when it has not just let out. It gets busy then. This attraction is a Star Tours/Body Wars type ride. They also have a "theater" where you sit on benches to watch the movie for those who can't handle the other show. I for one do not feel well after those rides, but last week when we went I let DD go in and I waited on the other side. After the show you walk through the "base station" and might see beluga whales, harbor seals, walrus, and polar bears. If it's a hot day, it's a great break from the heat!
Shark Encounter is very cool to walk through as well. The aquariums are all around you - you walk "through" them - almost like you are in a tube. When this is not busy it is great, as you can take your time. They have the "moving walkway" through part of it, and when it is crowded, you kind of have to go with the flow! The restaurant is nice too - you can see the fish while you dine.
Take a stroll through the Clydesdale barn. You can get your picture taken with the Clysdale (you can take your own - they take one too, but no obligation to buy). They have the Anhauser Busch Hospitality Center too - if the grown ups want to have a cold one!
As you can see, we like to "stop and smell the roses", and do not like to hurry around the park.
DD is not yet tall enough for Kraken, so we do not have to fit time in for that.. (she has 2" to go, and is counting the centimeters!)
I don't think I have left anything out.... if you have any other questions, feel free to PM me!