[GZG] Unexploded ordnance (Was: Mine resistant vehicles)

Back in the day, I was a keen SCUBA-diver, and it was common for
divers to bring up old weapons and munitions as souveniers from war-
time wrecks. Some, like old S&W revolvers were fairly benign, but
many sunken ships had 20mm shells, hand-grenades and mortar-bombs
scattered about like confetti. Once, on a beach in Cornwall, I saw a diver
whacking with a hammer...

An actual shell. About 100mm calibre, still attached to it's cartridge.

I left the vicinity. Hurriedly.