I sailed small Hobie Wave-a-Like catamaran from Tampa to Everglades city last March and I do a lot of cruising on my boat. I noticed that better to have couple of small drybags than one big. Wide, low profile plastic boxes even better.



Cheap tarp from hardware shop will keep you dry and protected, (I use same setup - tarp over boom) but it is noisy. Better to get softer fabric, lightweight vinyl coated nylon. I found oars very usefull navigating Everglades, it's surprisely easy to row catamaran - you can get a kit for whitewater catarafts here http://www.nrscatalog.com/dept.asp?deptid=229



Good luck!