...beofre I die, I want to crew on a snorkeling or snorkeling / kayak trip. I want to make sure everyone is seated OK for the sail out of the harbor. (On the Danger trip, everyone introduces themselves and tells where they are from). I'd point out things to sewe on the sail to the reef. (Younger crew cxan raise those sails) I particularly would like to do the reef talk - something about the area the passengers are going to be in, about their equipment, do's and don't's about the reef, and a reminder to make sure they are not too far from the boat and know where it is. What to do and not do if they have a problem.
I'd ask for weak swimmers and first time snorklers so that I could go into the water with them and make sure they are comfortable, then point out things they might not notice. Afterwards, I good offer drinks and in a spare moment ask where everyone is staying and if this is their first time to Key West and snorkling in the Keys, and undoubedly offer suggestions about where to have a drink or dinner, etc.
I'd do this for free once or twice on every trip if I could.
Or give a tour around the Hemingway House.