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

Water Breathing. The Garlic Shark can breathe only underwater.

Vampire Antipathy. Vampires, vampire spawn, and other similar creatures that come within 10 feet of the Garlic Shark must succeed on a DC 31 or be frightened of the Garlic Shark until the end of the creature's next turn.

Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 22 (3d10 + 6) piercing damage.

Stench. Any creature other than a Garlic Shark that starts its turn within 10 feet of the Garlic Shark must succeed on a DC 31 Constitution saving throw or be poisoned until the start of the creature’s next turn and take 1d12 Garlic damage.