Well, maybe more practical than silly but on both my cruises (and my upcoming one), I took large insulated cups. The drink glasses are small and I didn't want to have to keep getting up for refills, plus in the heat, the drinks warm up quick. A couple of bucks at Walmart made for a nice convenience.
Also, at pretty much any sports store that has diving gear/clothing, you can get small waterproof containers that come with a lanyard. They're great for holding cash, credit cards, sign & sail cards, etc. That way you don't have to leave your valuables on the beach when going for a swim. Best couple of bucks I ever spent