Going for a swim, hot tubs, water slides, diversions of any kind, can lead to things missing...if that's what you wanted me to say, I will tell you Ive NEVER heard of such a thing...having said that, keeping one eye on your stuff is NEVER a bad idea...and besides...there is NO point in bringing bling or anything valuable to the pool...although I have seen certain types in the hot tub with enough junque on em to drown em, and enuf makeup in 90 degree weather to melt aluminum. We generally leave whatever stuff we do bring (and less is more) right on the chaise lounge or table, in plain sight...mainly ours. Don't worry about towels and stuff, different lines have different systems for keeping track, up to and including not keeping track,,,dont take the ones from your room....fwiw, I have an old watch that I use at the pool, and we usually remove any rings that might come loose...you need NOTHING cept the card for the entire cruise...leave it all in the safe. (not counting shore stuff..) If your card is misplaced, or lost somehow, don't go looking,,,go DIRECTLY to guest services, in your swimmies...nobody cares... they'll nuke the old one and issue a replacement in a heartbeat... Frankly, I wouldn't worry about it. The fact that you asked shows you will take "reasonable care..." enjoy the cruise!!!!