Luggage and bags: waterproof bag with buckles that you can tie/snap around the canoe. lots and lots of little plastic bags to waterproof food/supplies and put garbage in--don't litter! & clean up after yourself! A small cooler is also extremely useful and will keep drinks nice and cooool even under the hot sun.
Clothing/Shoes/Weather Gear: pale, airy long sleeved shirts; long light pants; a wide brimmed hat; surf sandals that cover most of your feet but are good for withstanding water
Toiletries and Medical Supplies: HEAVY DUTY BUG REPELLENT! as in the back woods Off kind of stuff
Camping/Beach/Outdoor Gear: make sure your tent is 'no see um' proof. I bought mine at Wal Mart in Naples and it said it was, but it really wasn't. At sunset I got eaten alive and unwisely sprayed the tent with bug repellent (I'm sure that's going to haunt me healthwise)
You also MUST have a waterproof (laminated) map of the keys--!!! very important !!!
Miscellaneous: a wildlife guide--you'll see so many plants and exotic animals you'll be dying to find out what they are!!!
Toiletries and Medical Supplies: Make sure to get some mosquito repelant when you visit in the summer believe me...there can be a whole lot of bloodthirsty mosquitos that will eat you alive....and that itches !!