The search magnets / retrieval magnets have been specially developed for this purpose. An extra-thick steel casing ensures a strong concentration of the magnetic field and therefore additional adhesive force. In addition, the resulting higher weight of the magnet has the effect that the magnet is always perfectly aligned downwards when released.
You can use it to retrieve objects under water, e.g. from rivers, boat moorings, lakes, wells, etc. This magnet is often used for magnet fishing