Most people like to do the Dolphin swim first. Yes, you want to show up early at 8am and be first in line. That way, you check in first, and have a short wait at the snorkle station. They'll give you a bag that has a mask, snorkle (you keep it), and towels. They have sun tan lotion for you. All you need to bring is your credit card, license, underwater disposable camera, and rubber shoes you buy from
Walmart or Target. They'll give you a free locker to use. Then you get a wet suit, and find an area to sit. Head back to the beach of you want to be in the middle of everything. Stay near the dolphin lagoons if you want quiet, but your walk to everything will be farther. Most do the Coral Reef lagoon first.
There may be some people who go in at 8:30am who have the first swim of the day. So don't worry if the guy lets some people in and makes you wait until 9am.
This was our trip from 2001. Kinda outdated, but you'll get an idea of what to expect.
http://www.nogodforme.com/SeaWorld1.htm