Luggage and bags:
We flew into Key west from our home city were they don't mind to weigh our luggage. Once leaving we found out that our suit case weighed in around 90lb. (and we didn't wear 1/2 of it) after taking out our beach bags and random bags to stuff our junk in to comply with the 50 or 60 lb weight limit we finally were allowed to bored. If there is only 2 of you, take 1 suite case, if you bring more than that, you've over packed.
Clothing/Shoes/Weather Gear: If you travel anytime during the summer you really only need : swim suites, cover-ups,shorts, tank tops, tanning oil, sunscreen, camera and flip flops. Trust me, I live with an over-packer and we will be taking our 3rd trip there and finally he realizes that's all we wear. There's really nothing to dress up for. Nobody does!!!
water shoes - to protect from urchins, rocks etc.
Photo Equipment: I take my regular 35mm, and a couple of underwater disposible cameras. I nearly always use 800 or higher film. It works well outside and in. To get pictures for the computer, I just order a CD of my photos when I get them developed.
Camping/Beach/Outdoor Gear: snorkel/dive gear