I wouldn't worry too much. Just use common sense for the most part and you should be fine. When I went to the Caribbean last year, I had my 5Dm3, 24-70 (mk1), 70-200, 100mm, and a few other lenses.
The vast majority of my pictures were taken on the beach, including some where my camera was almost sitting on the sand trying to get angle shots. I would never change lenses on the beach -- I'd head back up towards the beach hotel we stayed at if I wanted to swap. I'd only set my camera down on my camera bag while I was on the beach, but even that was only a few times. And I never took my camera (and myself) into the water -- though I wouldn't worry about going waist deep if the waves weren't too much.
The best piece of advice I can offer is to watch the humidity. Our hotel room was air conditioned (thank god), and being on an island the humidity was usually close to 90%. With the temperature and humidity differential between our hotel room and the exterior, my camera and lenses would immediately fog up and be unusable for ~10 minutes once I walked outside, which would make it real difficult to run out and grab a shot if I saw something interesting.
So I would bring several large ziplock bags, put your gear in them before you plan on heading out, and let them sit outside (we had a secure porch area) so that your gear can get acclimated to the temperature. The bags will prevent some fogging, but will it will take longer for your gear to become acclimated.