Keys in August
I live in the Keys, but 30 mi below Marathon, so I dont know the waters up where youre going to be. But I can tell you that in my experience, once offshore , many of us fish and boat nude. If someone objects, they can up anchor and move ! Just dont anchor next to a oat full of kids unless they are nude too !!! There are lots of islands , especially ion gulf side, and there are often groups of nudists off to the side a bit. Just be cautious, keep your eyes on your depth finder, theres little sand or mud here, and coral is not friendly to lower units.
A few years ago, I did a good bit of sailing off Key Largo, on the Florida Bay side. Left the dock wearing shorts, once passed the ICW channel markers, and still in sight of the dock, stowed the shorts in the cabin for the day.
Also did a nude SCUBA trip with a small boat dive operator on Largo, out to John Pennecamp. I was the only customer-diver. The Divemaster/owner dove with me, but she wore a bikini. Their normal trip includes a thumb-drive full of photos, so she took quite a few of me during the dives.
Hired a fishing guide for a day on the flats. I had really wanted to ask if I could fish nude, but was hesitant, so I never asked him. Definitely a "wish I had" experience.