Whitsundays catamaran ?
We did that 2 years back with our Vanilla friends...had an awesome time. Once they hire the catamaran out to you they don't care of the shenanigans you're up to as long as you drop anchor at the said time and don't beach or capsize the vessel.
Sailing around the Whitsundays with our lifestyle friends will be great too.....please count us in if you plan one.
Loved it
We did the same, spent 2 weeks sailing around about 4 years ago with three couples, swingers and loved every minute of it, we decided to spend every second night partying ashore at a resort to keep things from becoming to close but the nights anchored out of site were so much fun.
Beautiful place to spend a couple of weeks and not that hard to sail one with some sailing experience, would love tio do it again.