Have you ever heard of the Plimsoll Line? If you aren't part of the world of shipping, you might be more familiar with the name "Plimsoll" used for a type of shoe (more on that later…)
The Plimsoll Line refers to the small circular image that appears on the hulls of ships around the world. The image — a painted circle bisected with a long horizontal line — is a marking that's designed to show whether a ship is overloaded. When the horizontal line is visible, the ship isn't at risk of sinking. If the line is not visible, well, there might be a problem.
The Plimsoll Line was devised by Samuel Plimsoll, an English politician and social reformer, who fought for merchant shipping regulation. Plimsoll's namesake load-marking image became mandatory on British ships when the United Kingdom Merchant Shipping Act of 1876 took effect. The Plimsoll Line later became standard worldwide.