Relo debuts in Chapter 235.
The turbulence of the sea, caused by the awakening of Kyogre and Groudon, is so powerful that it even forces Relo from the bottom of the sea to the surface. He is washed ashore and then burnt by the sun rays. From the back of Pilo, Sapphire sees him and swoops down to help him. As she does, a huge wave is about to crash and kill her, but Relo releases (invisible) energy, saving her life.
Winona believes that her attack broke the wave, saving Sapphire, but Sapphire correctly suspects that Relo was actually the one who did it. She heals his burns and decides to keep him temporarily as he heals, nicknaming him Relo.
Ruby arrives with Wallace and informs them that Relo, a Relicanth, has the ability to dive to the very bottom of the sea, where the Seafloor Cavern is located. However, he is only big enough to take two children: Ruby and Sapphire. The two set aside their differences and dive on Relo all the way to the bottom of the sea.
The author describes him: "The hardworking Pokémon is able to take humans to the ocean depths."
- Relo is about 80cm long