Beast of the Sea

Proficiency Bonus. The beast's proficiency bonus is equal to your proficiency bonus

Hit Points. The beast's hit points are equal to 5 + five times your ranger level (the beast has a number of Hit Dice [d8s] equal to your ranger level)

Amphibious. The beast can breathe both air and water.

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

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