Wereshark

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

Hold Breath (Hybrid Form Only). While out of water, the wereshark can hold its breath for 1 hour.

Shapechanger. The wereshark can use its action to polymorph into a Large shark-humanoid hybrid or into a Large hunter shark, or back into its true form, which is humanoid. Its statistics, other than its size and AC, are the same in each form, with the exceptions that only its shark and hybrid forms retain its swimming speed, and its shark form doesn't retain its walking speed. Any equipment it is wearing or carrying isn't transformed. The wereshark reverts to its true form if it dies.

Water Breathing (Shark or Hybrid Form Only). The wereshark can breathe only underwater.

Multiattack. In humanoid or hybrid form, the wereshark makes three trident attacks.

Bite (Shark or Hybrid Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 15 (2d10 + 4) piercing damage. If the target is a humanoid, it must succeed on a DC 14 Constitution saving throw or be cursed with wereshark lycanthropy.

Trident (Humanoid or Hybrid Form Only). Melee or Ranged Weapon Attack: +7 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 7 (1d6 + 4) piercing damage, or 8 (1d8 + 4) piercing damage if used with two hands to make a melee attack.