What is magnet fishing?

As the name suggests, magnet fishing is fishing with a magnet. However, a magnet fisherman does not fish for fish but for metal, hence the magnet ;).
What do you need for this? Mainly a good fishing magnet and a sturdy rope. Once the magnet is securely tied to the rope, you throw the magnet as far into the water as possible. Then you pull in the rope, and discover what the magnet has grabbed. Voila, from now on you are a magnet fisherman!