The Plimsoll line, painted on the side of a cargo ship, marks how deep it may legally sit in the water. It took Samuel Plimsoll years of shouting in Parliament about overloaded, overinsured “coffin ships” to get it made law in 1876, and even then the first version let each owner decide where to paint it. Only in 1890 did someone else start choosing the spot. The mark people tend to miss is the little ladder of lines beside it: one for summer, one for winter, one for the winter North Atlantic, one for the tropics, one for fresh water. A ship sinks a little lower in a river than at sea, because fresh water holds it up less, so the same hull carrying the same cargo can be safe in one place and over the line in the next. It’s a rule that only works because it never pretends there is one answer to how much is too much. It just asks where you are.