The mandatory equipment is a magnet with a holder (preferably UMP 75x25 [M10x3] GW F200 GOLD with Rope set price ~ 200 PLN). Without it, you won't go far ;)
Optional equipment includes:
Protective gloves. To avoid injury from sharp objects - they are included in the set,
Bucket / box / bag. So you have somewhere to put the retrieved items and take them home or to a collection container. Leaving a large amount of scrap on the shore doesn't look good. Responsible treasure hunters leave not only a clean river but also a clean shore,
Cloth for wiping hands and the magnet holder. This will extend the lifespan of the magnetic holder,
Steel hook. Heavier finds such as bicycles, motorcycles, or benches cannot be retrieved using a magnet alone - use a hook for the rope,
And if you have a hook, you'll need an additional rope to attach it.