If you have an EMS store by you, they carry great dry bags that pack tiny and flat. They are useful on have on the boat to keep your tip money, hat, and other small stuff dry. Speaking of that, bring a baseball cap so you can actually see when you're out in the sun and so your face doesn't burn. I don't like to use sunblock before diving because it gets in my eyes, so the hat is a must. When you're out on the water, your lips tend to get dry (at least mine do), so bring some chapstick type stuff with spf in it. Jolly Ranchers will win you friends on the boat during the SI. I bring a small save a dive kit in a zip lock bag with o rings, a spare mask strap, a few zip ties, a couple of snorkel keeprs, and a double ender. Doesn't take up much room and seems to solve most things that come up.
Have fun, and post a trip report when you get back
