As a kid, I grew up near minutes from the beach and many times saw grownups meticulously sifting through the sand with a metal detector. I imagined they were pulling up diamond rings and pirate's gold. My dad assured me they weren't, though I suspect he just didn't want to buy me a metal detector.
In any case, these magnet fishing hobbyists have them beat.
By dropping a very strong magnet underwater, history buffs "WW2 Wendal" fish their local lochs and rivers for valuable metal objects. They primarily explore WW2 sites for discarded war artifacts but often reel in non-military items such as stolen safes and, well, junk. Sometimes they find nothing at all but, judging from their videos, that doesn't break their spirit.