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Tentacool resembles a box jellyfish. It has a light blue, clear body with two large, transparent, red crystals on each side of its body, and one small one in the middle. It has two small eyes with black pupils and no visible irises near the base of its body. It has two tentacles laced with stinging cells. The tentacles extend from beneath its round, blue lower body, which has a cape-like formation in the back.
Tentacool absorbs sunlight and refracts it using water inside its body to convert it into beam energy, as seen in the anime. It is also able to control Pokémon it touches with its tentacles. Tentacool can be found throughout the ocean. It will sometimes wash ashore and become shrivelled and dehydrated, but may be revived if it is thrown back into the ocean.