Disney does not have a shuttle service to Sea World. However, you can make arrangements with Mears Transportation Service, they do run a shuttle for a cost of about $16 round trip per person . A town car service can be used, the cost would be about $65.00 roundtrip plus tip, or you can rent a car from either the WDW Car Care Center or from one of the DTD resorts, I would think that the cost would be around $60 maybe less.
another option is orlando's public bus, the LYNX ( http://www.golynx.com ). the #50 route can be picked up at the TTC and includes a stop right outside Sea World. $3 per person roundtrip.
Well depending on how many in your group you could use Transfloridian, it would be about $55 give or take roundtrip. Cheaper than mears would be and it's a private shuttle. I've used them before, you should call and reserve because they do get busy since they do alot of transfers between here and south florida.
I like the idea of the public bus, any idea how long it would take to get to there from TTC? Also, anyone know how I would get to TTC from Pop Century? May be worth it to take the last posters option for $55. Beats renting a car and worrying about car seats and all.