We also bought cheap water shoes (on line from a couple of aquatic sites, since we refuse to set foot, aquatic or otherwise, into a WalMart - destroyer of small town businesses) which we used on the cruise and then just left on board. I also had Teva's but did not wear them in the water, since they would not protect my feet from coral cuts and tend to slip a bit in water. I did wear them on board and on land. Better than regular flip-flops for moderate hiking.

If you have any problems with vertigo or similar phobias regarding elevation, proximity to cliffs, hyper-testosteroned guides driving jeeps on the very edge of reason (we found that to be the most fun part of the tour but that may just be us, since our driver looked like a young Tom Cruise with very cool Polynesian tattoos on his shoulder and thigh...), you should decline the more radical 4X4 trips. They are not for the faint of heart.

We always left the umbrellas in the cabin, determined that if it rained, we would just get wet and would thereafter dry quickly, since we were only wearing t-shirts and cargo shorts.

Cheers, Fred