While on-route to the island where only the Dragon Pokémon Kairyu live, Goh encountered a Dewgong that he tried to catch. He had brought an entire backpack of Poké Balls to catch Pokémon that day but he ended up using all of them to finally catch Dewgong.
Ash and Goh rode on its back to try to get to the island but a female Dewgong swam by which got Goh's Dewgong
infatuated with it and it started going after her but right into a storm. Ash and Goh got knocked off and into the sea but thankfully a ground a Dragonite rescued them. Later on at the island, Goh noted that Dewgong was still heartbroken.