A few additional suggestions:
-20-40lb magnetic hooks. We used them for the first time on our last cruise and they are great...hang hats, wet bathing suits, backpack (empty), toiletry kit, etc. We even used them to hang some xmas lights (cruise was right before Christmas)!
-Towel clips for chairs on the deck
-if you’re a drinker, a good beer coozie and or insulated cup for cocktails