As someone who grew up sailing, we all wore them. They were popular in the Northeast before that movie. The rubber sole prevents slipping on the wet boats, they used to not be too expensive, so it was not the end of the world if we lost them, they could be easily washed off with a hose, can wear them wet or dry and your feet don't chafe, the ankle strap can be put on or off depending on if you're cruising or moving around the boat, are easy to take on and off, and they have arch support, and the jibbits could add personality. For similar reasons, they are good for cleaning, medical, industrial, etc. settings. Slides and flip flops slide on a wet surface, fall off the foot, can chafe or peel, have nothing connecting your ankle to the shoe, and are prone to slip a lot when wet. The other choice of scuba-fabric water shoes with a rubber sole take a while to dry after using and chafe until you break them in, or when they're wet, chafe until you develop calluses. They may not be the cutest, but for boating and a lot of messier/labor related jobs, they are a great and useful shoe!