Using a Rare Earth Magnet

I made a 12 X 6 inch magnet using about 8 "blocks" of material from a mining site. I enclosed it in aluminum. Rare earth ? Anyway - I have not used it in water as here in the desert there's very little but have used it extensively at old housing sites - especially alnong the railrtoad lines. We dig old dumps and I drag it through the earth and way undert trees & bushes, finding a lot of goodies. I have a strong rope on it.
If under water I would think It would be smarter to use a nylon line. Steve in so az

I've got a rare earth magnet? about the same size as yours Steve I use in the Mississippi, found anchors, steel pails, steel fishing rods, small punt gun , lanterns ,bicycles, log chains. So I've got alot time on my hands I use kevlar cord if I get stuck on something bigger than I am I cleat it off on the transome either get the object or pull it loose. Doesn't have the same draw as Mding though. I get bored trolling for walleyes we hit the back waters with the magnet & troll for junk LOL
Tim