The main thing I think about when I am packing for a trip is: What can I not get on location?
My father, an experienced diver for 20 years, at one time had a Nikonos (Nik III, if I recall) about a decade ago for a couple years; and I serviced it for him.
My advice: Carry along extra anything that corrodes. Also, carry Q-tips & 91% rubbing alcohol, and pencil erasers to clean electrical contacts.
Make sure your battery charger has the right plug and voltage for your destination hotel or live-aboard. Along these lines, be aware that AA NiMH batteries self-discharge 10-20% every week (more if the batteries have a bunch of charge cycles on them).
Keep one complete set of alkaline batteries still in the pack (Shop-Rite often has 8 AA's or AAA's for 99 cents), in case the charger fails: Oftentimes, electric utilities on small islands get all sorts of transients, frying sensitive equipment. Been there, done that, have the T-shirt. 
Whenever I go on a remote shoot, I always buy a new branded CF card (Lexar or San Disk) from a major retailer [NEVER buy a CF on eBay -- Almost all are counterfeit, according to surveys & tests published a month or two ago in Shutterbug or Pop Photography (I forget which).]
Also, carry a cheapie spare P&S camera: The cost of airfare and accomodations gets thrown out the window if your camera floods/ gets sat on/ gets dropped... on the first day. If you never take the camera out of the sealed box, reputable dealers will take it back in 14 or 30 days.