I see no one has mentioned WET WEATHER GEAR for all. It's a must have on all trips no matter where you go or for how long .. as is a full set of warm stuff per person (including for your head).
We use Kathmandu rectangular suit cases. They aren't really solid, but they can be folded flat when not in use and have a wire inner that holds the walls up when in use. Sale had them at $20 each, but they can be found at $60. Zipper all the way around the top, clear window on one side of the top flap (who knows why) and we keep them in our pull out under bed draw as they are a perfect height.
I'm usually in thongs (the foot wear kind), but always take a good pair of walking shoes and decent socks. Several pairs of undies (if you wear them) and socks are a must - at least 2 pair a day in case of inclement weather or water crossings.
Two towels each. One for showers. One for swimming. Don't forget a hat or two either. A cap for quick use and one wide brimmed for walking through the day. We also have a "day pack" to carry things whilst walking that can fit extra clothes, towels, food, cup and water, wallets, watches and keys (when swimming). I also take a camera bag with me everywhere, so the camera is usually around my neck and this leaves some extra storage in there for keys and wallets on shorter walks.
But I'm with the others though, who utilise (protective) clothing only when required or in company. Dare To Be Bare!!
Kit_e