Whenever you watch a film or TV show set on the high seas, there will invariably come a time when a sailor is ordered to “swab the decks”. But what does that actually mean?

This video explains exactly what it means to swab the decks, and why it was such an important part of being at sea that it’s always mentioned in movies and TV shows about seafarers.

Sailors would swab (or mop) the decks with saltwater. That would stop fungus from growing, and cause the wood to swell, preventing leaks.

So, if no one swabbed the decks for a long time you’d end up with a sinking ship full of fungus. Which wouldn’t be a pretty sight.