No. While magnets are typically coated with nickel, zinc or epoxy to protect them against rust and corrosion from moisture they are not waterproof.
Neodymium magnets will work wet or submerged for a short period. Any water penetration into the magnet, however, will cause a slow deterioration of the magnet’s magnetic field and cause rust to leak from even the most microscopic scratch or aberration in the magnet’s outer coating.
If you are looking for waterproof neodymium magnets, check out our Sewing Magnets. These magnets are encased in a waterproof PVC pouch that protects them from moisture.