I love Sea World,it's only about 10 minutes away so it's very close to Disney and definitely worth a visit.It is somewhat different from the Disney parks as there are a lot of shows you have to schedule your day around,a lot of animal exhibits and interactions,a nice kids area and a couple of rides 2 of which are major rollercoasters.The penguin exhibit is currently closed as next year they're opening Antarctica a new themed area to incorporate the penguins along with a new family thrill ride.It however is not a small park and given that you have a lot of shows at different times Sea World is easily a 2 day park.
Aquatica right now is my favorite Orlando waterpark,it has a South Pacific theme,more palm trees and less trees than the Disney waterparks so less shade but it has a lot of pluses.For example they have two kids areas,one for bigger kids that's even fun for adults,their fast lazy river you can't find at Disney and is easily the coolest attraction there.Shopping and dining options are better at Aquatica than the Disney parks,it has two huge wave pools and a lot of fun slides.All three waterparks have things that I like so even though I prefer Aquatica,they're all very close.