Blood Frenzy.

The blademaster has advantage on melee attack rolls against any creature that doesn't have all its hit points.

Limited Amphibiousness.

The blademaster can breathe air and water, but it needs to be submerged at least once every 4 hours to avoid suffocating.

Shark Telepathy.

The blademaster can magically command any shark within 120 feet of it, using a limited telepathy.

Multiattack.

The blademaster makes three attacks with its wavecutter blade, or one attack with its bite and two with its claws.

Wavecutter Blade.

Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 12 (2d8 + 3) slashing damage.

Bite.

Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 8 (1d10 + 3) piercing damage.

Claws.

Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 3) slashing damage.

Sahuagin Blademaster