I do almost the exact same thing as Oh Liz..... and I'm sorry-i personally would never bring a laptop unless i HAD to do business...There is so much more I d rather be doing then doing what I normally do at home..ie. Be on the computer....People really need to "un-plug" once in awhile.....I have my Jam phone that people can get ahold of me if need be-Would never use my American phone-insane roaming fees, long distance costs..

Regarding liquids-alot of things can be purchased in Jam...
Snorkel gear-I'd rent it...
Books-that can be difficult-I love to read- so try to take one large softcover...
Towels-I use the ones where ever am staying-if i need a Big one-I purchase from vendours and will leave with a friend (if I cant fit it in my suitcase and my friend wants it-)
Camera and my mini ipod sysytem-all goes in my backpack that goes under my airline seat..

I think you can do it Gerry.....