The Mikan Gym has a curved roof and was shown to have automated features, such as moving walls and floors. Its standard battlefield can also transform into a pool. The beach near the Gym is also buoyed off for Pokémon Surfing races.
The interior of the Gym is built for a Pokémon water battle, much like the ones in Cerulean City, Sootopolis City, and Pastoria City. However, it is also used to ensure that all Water Pokémon have an equal standing while they compete in the Water Gun match-up, where a Pokémon's accuracy and speed is tested. The Pokémon who shoots down the most targets wins.
The Mikan Gym's final challenge takes place outside with a Pokémon Wave Ride. The race requires that both Trainers surf on top of a Pokémon out into the ocean where they must go around a designated buoy and come back. Physical contact between competitors is allowed. A challenge may be ended if a competitor falls into the water. As shown in the anime, a rogue wave can prove a hazard for both the Pokémon and their rider, although a skilled surfer may be able to use the waves to their advantage.
Pokémon used in Gym
Cissy used Seadra against Ash's Squirtle for the Water Gun skeet portion of their Gym battle. It seems to be sensitive, as it fired a Water Gun at Ash after he called it ugly. It tied with Squirtle in the amount of targets it hit, resulting in Cissy deciding to settle the match with Wave Ride.
Cissy chose Blastoise to use in the Pokémon Wave Ride portion of Ash's Gym match with her. It was temporarily captured by Team Rocket but it escaped from them easily by using its overwhelming strength, and sent the trio blasting off with its powerful Hydro Pump. Blastoise was set against Ash's Lapras for the Wave Ride. What Lapras had over it in speed, Blastoise matched with strength. Cissy's strategy was to have Blastoise ram Lapras from the side in order to knock Ash off and give her a clear lead. As Cissy and Blastoise were nearing the finish line, a tidal wave came upon them. While Ash was saved by Lapras's Ice Beam, Cissy was knocked off Blastoise when the wave hit. Blastoise moved quickly and saved Cissy from falling in the water. Even though they caught up with Ash and Lapras, Ash still managed to cross the finish line first by having Lapras use Ice Beam and riding on the ice.