I live by The Thames; for the last few days, we've had magnet fishers on the bank. I gather this crew have fished up a cannon and a sawn-off shotgun, as well as

I live by The Thames; for the last few days, we've had magnet fishers on the bank. I gather this crew have fished up a cannon and a sawn-off shotgun, as well as stuff like jewelry. I'm not going to link to them (Facebook <spit>), but you can search for "Northants magnet fishers". They all seem to use the same magnets, which look as if they're about 3" diameter, 2" tall cylinders. It seems to require a fair bit of muscle to separate the dredged iron from the magnet. I don't know where they get these magnets.