Keep a set of swimwear in your car. If you go to a place and forgot your swimsuit? Got the backup. Go to a hotel and find out they had a pool you didn't know about? Backup in the car. Accidentally shit yourself? Got at least something on you. Do I shit myself enough to worry about it? Not since I was a baby but now I know I got swim trunks in my car just in case.
This works for so many occasions too. At a watermelon eating contest? Backup in the car. Going to a funeral? Backup in the car. Need to bury a body? Backup clothing, right there.
Not recommended for lycra or spandex suits, or any suit that has elastic closures, particularly during the summer months. They will rapidly degrade in the heat of the car. My wife left hers in the car after a vacation (never used it). It was tucked in the trunk. Found it a month later and it disintegrated in the wash.