They are all SEPERATE!!! Each one is of it's own entity............ meaning they are not connected at all. Universal Studios is one park, Islands of Adventure is one park, although they are owned by the same company, and they are located next to each other, you would still need to purchase tickets for BOTH parks if you want to go to both parks......... therefore you can "hop" between them, HOWEVER, they are each their OWN park. Same as Disney, Magic Kingdom is one park, Animal Kingdom is one park, MGM is one park............etc.... you have to buy tickets to EACH one, but also with those parks you can "hop" from park to park....... but you still have to buy INDIVIDUAL tickets to each park..... they have "park hopper" tickets for sale.
I think the ONLY park associated with Seaworld............ which is one park, is Busch Gardens, which is one park....... and NO you can't really do both in one day........ as one is in Orlando and one is in Tampa Bay........ I'd do a lot more research if I were you before you decide on buying any tickets!!!!!!!!!!!!!!!
Good Luck