Magnet fishing is a growing hobby that involves using a long rope and strong magnet to retrieve lost or hidden metal objects in water. It can help to clean up waterways and improve the environment by removing discarded trash.

Magnet fishing is possible because water does not block or weaken a magnetic field, so the magnet will attract objects as usual underwater. But if the object you're trying to attract is heavy you need a strong magnet.

Drop paper clips into a clear container full of water and verify that the attractive force of your magnet is the same inside and outside the water. If you don't know how to measure the strength of a magnet read this article.