Tentacool is a small, jellyfish-like Pokémon. 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. Near the base of its body is a pointed, beak-like projection and two eyes with small pupils. There are two grayish tentacles extending from beneath its round lower body, which has a cape-like formation on the back.
Tentacool's entire body is made of 99% water, and the remaining 1% contains the organ that produces its poison. It absorbs sunlight and refracts it using the water inside its body to convert it into beam energy. Its tentacles are laced with stinging cells and, as seen in the anime, it can control Pokémon it touches with its tentacles. The tentacles break off occasionally, but they can regenerate. The poison from its tentacles is so potent, that someone would need to be immediately rushed to the hospital. Tentacool is not a very strong swimmer, traveling throughout the world using ocean currents. Tentacool searches for food while drifting on the surface of shallow seas. Tentacool can blend in the water, making it very difficult to spot. It will sometimes wash ashore and shrivel up due to dehydration, though it remains equally as dangerous. Tentacool may be revived if thrown back into the sea.
In Tentacool and Tentacruel, multiple Tentacool had been attacking Nastina's construction site. She subsequently made a public announcement offering one million dollars to anyone who could exterminate them. Team Rocket took up her offer but were quickly surrounded by a huge group of angry Tentacool, one of which evolved into a giant Tentacruel. It subsequently went on a rampage before being stopped by Misty.
In Pikachu's Vacation, a Tentacool was at the Pokémon Theme Park.
In Friends to the End, a Tentacool was seen during Ritchie and Assunta's battle, but it is unknown who it belonged to. In the same episode, another Trainer's Tentacool attended the closing ceremonies of the Indigo Plateau Conference.
Multiple Tentacool appeared in Bye Bye Psyduck.
In The Power of One, multiple Tentacool sensed the disturbance caused by Lawrence III.
A wild Tentacool appeared in Pikachu's Rescue Adventure.
A Tentacool appeared in a fantasy in The Totodile Duel.
In Hook, Line, and Stinker, a Trainer's Tentacool competed in the annual Seaking Catching Competition.
A Tentacool appeared in Snorlax Snowman.
A Tentacool appeared in the opening intro of Celebi: The Voice of the Forest, which was reused for Pokémon Heroes: Latios & Latias.
In The Joy of Water Pokémon, a Tentacool lived in Lake Lucid.
In Mantine Overboard!, two Tentacool lived in the sea near Ogi City.
In The Legend of Thunder!, a Tentacool lived at a Pokémon Center.
A Tentacool appeared in Pokémon Heroes: Latios & Latias, under the ownership of a competitor in the Tour de Alto Mare.
Multiple Tentacool appeared in Destiny Deoxys.
In a flashback in A Cacturne for the Worse, May was scared by multiple Tentacool due to being surrounded by them at one point in her childhood. This had resulted in her mother attempting to catch her after mistaking her for a Tentacool.
A Tentacool appeared in the opening sequence of Lucario and the Mystery of Mew.
In Once More With Reeling!, a Coordinator's Tentacool competed in the Terracotta Contest.
In Up Close and Personable!, a Tentacool lived in the lake near the Pokémon Summer Academy.
Multiple Tentacool appeared in Kalos, Where Dreams and Adventures Begin!.
In Going for the Gold!, two Tentacool were exhibits in the Ambrette Aquarium.
Multiple Tentacool appeared in Diancie and the Cocoon of Destruction.
A Tentacool appeared in a flashback in Day Three Blockbusters!.
A Tentacool appeared in The Island Whisperer!.
Multiple Tentacool appeared in I Choose You!.
A wild Tentacool appeared in Alola, Kanto!.
In I Choose Paradise!, two Trainers' Tentacool were at the Pokémon Paradise Resort.
Five Tentacool appeared in Legend? Go! Friends? Go!.
In The Sinnoh Iceberg Race!, Goh attempted to catch a Tentacool out of a horde of them, only for it to dodge the Poké Ball, resulting in Goh catching a different Tentacool instead. Goh's Tentacool has since made further appearances in Pokémon Journeys: The Series.
A Tentacool appeared in Getting More Than You Battled For!.
||Tentacool, a Jellyfish Pokémon. 99% of its body is made up of water.
In File 4: Charizard, Red caught a Tentacool after passing by it.
In The Cavern, a Tentacool was in the waters that surrounded the Seafloor Cavern.