you can also take a Mears bus. they will pick you up at your resort and pick you up a Sea World at a designated time. The price is $15 per person round trip. I believe kids under 5 ride free (but dont quote me on that) I have a 2 and 3 year old and they were both free.
Depending on how many people you have it can be cheaper to take a van taxi. It cost us about $35 each way but with 7 of us it was a bit cheaper than Mears. Figure $80 round trip by Taxi (with tip). Anything over 5 people and you save money on the taxi and don't have to wait for a Mears Shuttle or share it with anyone. Just a thought...
Little more expensive that I thought, we're planning on getting a car for when we go to clearwater, maybe we'll just plan on an extra day with the car.