Werefish

Shapechanger. The werefish can use its action to polymorph into a fish-humanoid hybrid or into a giant phiranna, or back into its true form, which is humanoid. Its statistics, other than its AC, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Amphibious. The werefish is amphibious in hybrid form, and can only breathe water is its fish form.

Multiattack. (Humanoid or Hybrid Form Only). The werefish makes two attacks: one with its bite and one with its fin slap.

Bite (Fish or Hybrid Form Only). Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) piercing damage. If the target is a humanoid, it must succeed on a DC 12 Constitution saving throw or be cursed with werewolf lycanthropy.

Fin Slap. (Fish or Hybrid Form Only). Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 7 (2d4 + 2) slashing damage.

Trident (Humanoid Form Only). Melee or Ranged Weapon Attack: +4 to hit, reach 5 ft. or range 20/60 ft., one creature. Hit: 5 (1d6 + 2) piercing damage, or 6 (1d8 + 2) piercing damage if used with two hands to make a melee attack.