Using a metal detector?
Did a few miles with a metal detector and have several notes to share:
1) They need to make fiberglass insoles with built in metal detectors. Ear phones - left covers left foot, right covers right foot.
2) Guys leave behind a lot of empty cans. You may find a lot of nails, bottle caps, pennies, and pull tabs. Fewer bolts, clamps, pennies, and various pieces of metal.
3) Using a detector really helps one look for venomous snakes.
4) Seems to eat up 9 volt batteries a little too fast for my tastes. Perhaps turning down the sensitivity would help? Reading the manual for tips on that now.
5) Real bumpy roads offer the most stuff. More heavily used bumpy roads will give plenty of readings but the metal always seems to be buried. A problem on a real rocky road.
6) Bring a good magnet, 6" shovel and 4" rake.
It is reasonable entertainment and will certainly help one find many lost items. You'll find plenty of stuff anywhere humans have frequented. The more people, the more stuff.
I think one actually could find some coins and rings on public beaches.
Half decent detectors are pretty cheap these days. I'd call it cheap entertainment and good physical and mental exercise.
Would be awesome working old battlefields.