We loved parasailing at
Castaway Cay, it was beautiful.
They will give you a time to meet at the dock and you'll be on a boat with a total of 10-12 people. Typically you ride tandem and you spend about 10-15 minutes total in the air, including going up and coming back to the boat.
Unfortunately this excursion does get cancelled often because of high winds. I do highly recommend it.