goofy4tink has a good link about the bus
I got the bus at DTD. Don't do that in the morning. The Disney buses only stop at the Marketplace side early in the day, so I had to walk clear across DTD past the big Cirque tent to get to the bus stop. I was alone, and wasn't crazy about being in a fairly large parking lot by myself. Use the TTC stop.
There were a few stops along the way, and I'm guessing it took 30-45 minutes to get to Sea World. (I think the wait at the bus stop was close to 15 minutes.) They let you off on a "city" corner, and it's good hike across the Sea World parking lot.
And when you're leaving Sea World, you go back across the parking lot to wait for the bus. I accidentally got on a local trolley, so pay attention or confirm with the driver that you're on the right bus heading for DTD or TTC.
At the end of the day it worked out well because I got off at DTD and used the Planet Hollywood coupon for dinner that is part of the basic resort package.
Bottom line. . .1. I'm not sure it's the ideal if you have kids, but for adults not minding a bit of an adventure, go for it. 2. do lots of research on the bus schedule ahead of time.