For those hot sultry days to sunbathe and keep cool. For those cool nights fishing bait. Several cheap towels or rags to wipe fish slime off hands. HATS - Wide brim, baseballs caps, foreign legion, etc. Security straps are also recommended to prevent loss over the side.
Staterooms contain an electrical outlet for hair dryers, electrical razors, etc.
Video recorders are also welcome. A good selection of VHS tapes usually exists, but you re more than welcome to bring one or two along to share. Not necessary for shorter trips. Your local pharmacists would be another excellent source for recommendations.