Homebrew, Ravenloft: Denizens of Darkness (3.5e)
Shapechanger. The wereray can use its action to polymorph into a ray-humanoid hybrid or into a stingray, or back into its human form. Its statistics, other than its size, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its human form if it dies.
Amphibious (Hybrid & Stingray Form Only). The wereray can breathe air & water.
Swimby (Hybrid & Stingray Form Only). The wereray doesn't provoke opportunity attacks when it swims out of an enemy's reach.
Multiattack (Humanoid or Hybrid Form Only). The wereray makes two attacks, only one of which can be a bite.
Bite (Stingray or Hybrid Form Only). Melee Weapon Attack: +4 to hit, reach 5', one target. Hit: 5 (1d6 + 2) piercing damage. If the target is a humanoid, it must succeed on a DC 12 Constitution saving throw or be cursed with wereray lycanthropy.
Harpoon (Humanoid or Hybrid Form Only. Melee or Ranged Weapon Attack: +4 to hit, reach 5' or range 20'/60', one target. Hit: 9 (2d6 + 2) piercing damage. If the target is a Medium or smaller creature, the wereray can pull it 10' closer.
Tail (Stingray or Hybrid Form Only). Melee Weapon Attack: +4 to hit, reach 5', one target. Hit: 6 (1d8 + 2) piercing damage. The target must make a DC 13 Constitution saving throw or be paralyzed for 1 minute.
Undersea Camouflage. The wereray can take the Hide action on its turn if there are sufficient visual obstructions, such as foliage, murky water, or a sandy sea floor.
Coastal, Underwater