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

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

Whirlwind (Recharge 4–6). Each creature in the elemental's space must make a DC 13 Strength saving throw. On a failure, a target takes 15 (3d8 + 2) bludgeoning damage and is flung up 20 feet away from the elemental in a random direction and knocked prone. If a thrown target strikes an object, such as a wall or floor, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 13 Dexterity saving throw or take the same damage and be knocked prone.