I tie a dumb key with the drawstring of my bathing suit. It stays safely tucked against my waist. Though there was the one time that the drawstrings knotted up when I tried to take my key off my swim shorts, and then my phone in the car started ringing, so I tried to open the car door with a key tied to the front of my swim shorts with approximately zero inches of drawstring slack, and the lock was being difficult, then the car alarm went off, and well, let's just say that the whole debacle was... less than dignified. I did eventually get the door open and the alarm off, but that was the last time I did not fully release the key from my swimsuit prior to unlocking the car. My supply of holes to jump in upon such embarrassment is limited.