I've got something to help you understandIn fiction, it's common to see people on beaches looking around for stuff using metal detectors. This often carries the stereotype (in Britain at least) of someone who searches the countryside hoping to find buried treasure (not as silly as it sounds, since hauls of artifacts made of precious metals are occasionally found in Britain, which is what leads to this kind of behaviour in the first place). It's technically legal (and landowners have a good incentive, since they're entitled to a share of whatever's found on their land) and there are even specific laws for finding buried treasure (technically it belongs to the crown, but the finder and landowner will be paid a fee from whatever museum that ends up taking it), however for obvious reasons it greatly annoys actual historians and archaeologists, who'd rather see the sites properly excavated rather than plundered. This trope is not limited to beaches. See also Metal Detector Puzzle when this occurs in Video Games. Occasionally seen in Beach Episodes. Note, that in Canada, the long running TV series, Beachcombers had the starring character, Nick, in an entirely different version of this activity. Namely, it was professional lumber salvaging using boats to haul lost logs into the water for towing to timber companies to looking recover their lost materials.
Something waiting there, beneath the sand
My metal detector is with me all of the time
I'm the inspector over the mine
They Might Be Giants, "Metal Detector"
Examples:Comic Books Fan Fic