Tentacool debuted in The Sinnoh Iceberg Race!, where Goh caught it while he and Ash came to Vermilion City. When Ash and Goh arrived in Vermilion Harbor they found a school of Tentacool. Ash was excited by the group of Jellyfish Pokémon and poked one, who lashed Ash with a Bubble Beam on the face. Goh decides to caught a Tentacool. He threw a Poké Ball, but the Tentacool dodged the ball, causing this one to get caught instead.
After it was caught, Tentacool was left at Cerise Laboratory, along with Goh's other Pokémon as seen in Finding a Legend!, Best Friend...Worst Nightmare! and Raid Battle in the Ruins!.
In Panic in the Park!, during the food crises in Cerise Laboratory, Goh commanded Tentacool and his Dewgong to use Ice Beam in the floodwaters to help him save his Cascoons. In JN031, Tentacool was seen in the water alongside with Goh's other Water-type Pokémon.