Plimsoll is a type of shoe that was originally designed for sailors. The name comes from the line on the side of the boat, known as the loadline or waterline, which indicated how deep in the water the ship could float without sinking. The shoes were made with a rubber sole and canvas upper to make them lightweight and easy to clean after being worn on board ships. Over time, the term "plimsoll" has come to refer to any type of low-cut shoe that is suitable for outdoor activities or sports.