Trident of Fish Command

This trident is a magic weapon. It has 3 charges. While you carry it, you can use an action and expend 1 charge to cast _dominate beast_ (save DC 15) from it on a beast that has an innate swimming speed. The trident regains 1d3 expended charges daily at dawn.

Source: 5e Core Rules · OGL-1.0a · 5.1