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.