If you have 3-pin 240V shore power sockets on board, seal them with a plastic blanking plug of the type used to stop children electrocuting themselves when youre sailing offshore…
Try to flush your outboard engine through with fresh water when you come off the boat, and check your anodes frequently. You won't know about it until it's too late!
Starting the engine while shore power is still attached can damage your charging system (older boats mostly)
Most suntan lotions take between 15 minutes and an hour to become active. Always apply early.