what I think you might be looking for is a "Booze Cruise" a boat ride, bunch of people,free jugs of rum punch, Red Stripe, Music........whatever else ??
Look for one that goes out for a ride that includes sunset........if its still running there is a "Cat" sailboat that has such a thing, from the beach in Negril (ask around, or someone may chime in),......... unless you are sure of the weather, and your confident that you will want to go when the day arrives, forgo any "deposit" just show up or call a few hours before departure time, .......99.9 % of the time they have plenty of room for 2 more.......enjoy
"Stay Warm My Friends"