Encrypt the thumb drive. If someone breaks into the
boat they may grab the grab bag (electronic$ in it) and the last thing you want is to add identity theft to that.
Hurricane matches (waterproof matches) also can and will self-combust. If you pack them, pack them in a metal 35mm film can (if you can still find one) or similar container that excludes oxygen and won't melt if they light up.
fwiw.