My DD went when she was 6 and had a blast! You meet over at the GF marina about 15 minutes prior to sailing... so about 9:45. The kids are fitted with their life preservers, and given pirate bandanas to wear. The parents sign a waiver at that time, giving permission for the child to go, etc.
The excursion lasts about 2 hours, and the kids sail to the beaches at the Poly, Contemporary, and WL to search for pieces of the treasure map. Once these are found, they sail over to Fort Wilderness, near River Country to dig for buried treasure (it really consists of party favor type toys). Then on the way back, they have a snack, and when they arrive, they split the booty.
The trip is supervised by 4 adults that work in the Child activity department, and 2 of them are certified lifeguards. The person in charge is Drew, and he is WONDERFUL!
It is a great time for the kids to do their own thing, and let mom and dad get a little alone time, as well!