It's a beautiful thing instead of a cab and you save your $$ for souvenirs! Go to the Transportation Hub at Disney and a Lynx bus will be there. We actually took the bus from our resort to the Trans Hub which is right by MK.
The #50 bus runs to Sea World every 20 mins or so and will drop you off across the street!
When SW closed we crossed the street and waited 5 mins and there was the bus again ready to take us back!! We paid $1.75 for adults and less for the kids I think. (each way) Clean bus too--glad we didn't cab it!
GOOD LUCK!!