Bullets shouldn't be magnetic since they are made of brass, copper and lead, but I guess these ones had enough rusty ferrous material stuck to them that I pulled them out with a magnet anyway.
The little rod below the horseshoe is also entirely made of copper and not all magnetic, but it was held on to the magnet by some rusty scrap.
I also got a fair amount of loose change, and what I think is a door knob that I was a little worried could be a grenade when I pulled it out amongst the bullets.
The rusty lock and chain are intriguing. Maybe someone was executed by chaining their hands and throwing them into the canal.