Magnetic
I went “magnet fishing”, this is where you simply tie a strong magnet to a rope and throw it in ponds and pools until you find some metal stuff on the bottom. Mostly you will find junk and bikes and shrapnel. But I live in Belgium, near Ypres where there have been great battles in WWI, and I just threw the magnet across a small pond just outside the city. And believe it or not, I surfaced a grenade.
Navarro13