Metal detectors at the beach

Do you ever encounter some false beliefs retained from your childhood still not cleaned out from your brain? Today I saw a man using a metal detector at the beach, and I thought, "Ah yes, he's looking for buried pirate treasure." And then I thought, "Wait no that doesn't make sense. What the fuck is he actually doing?" And then I had to learn the real reason people use metal detectors at the beach

Somewhat related: http://www.paulgraham.com/lies.html