When delving into the secret areas of Bubbly Basin, the latest area in the Pokopia Expansion Pass, you find an old Pokemon Gym. At the base of the gym, there are pedestals waiting for you to add their display items. This is the perfect place for the Mermaid's Gym habitat, home to one of the original water Pokemon, Starmie. To complete the habitat, you'll first have to find the six Decorative Poke Balls scattered across the Bubbly Basin.
