Beast of the Sea

The beast can breathe both air and water.

You can add your proficiency bonus to any ability check or saving throw that the beast makes.

Melee Weapon Attack: your spell attack modifier to hit, reach 5 ft., one target. Hit: 1d6 + 2 + PB piercing damage or 1d6 + 2 + PB bludgeoning damage (your choice), and the target is grappled (escape DC equal to your spellcasting save DC). Until this grapple ends, the beast can't use this attack on another target.