An aquator is one of the most dreaded of the upper dungeon enemies. Its attack will rust and degrade any metal armor that is not greased or rustproofed. Aquators cannot climb ladders, so climbing up a ladder yourself and shooting them with a ranged weapon from above is one way to deal with them.
They will usually carry a thoroughly rusted items inside their body, frequently a helmet of large size. These items can be extracted when the aquator is slain.