Humilau City Pokémon Gym Gym Leader: Marlon "More Splash than the Sea"
Before being able to challenge the Gym, the player must first go find Marlon, who is off swimming at the moment. He will pop out of the water once the player tries to pass the first house north of the Gym, after which he'll return to the Gym.
The Gym is a designed somewhat like a bog, with tall grass and lily pads in the water, also decorated with several fountains. The player must move from one wooden platform to another by floating on the lily pads, eventually reaching Marlon at the end of the Gym. After Marlon is defeated, he will hand out the Wave Badge and TM55 (Scald), after which he will jump off the platform and swim away. The player can then ride a lily pad straight back to the entrance.
The Humilau Gym appeared in The Road to Humilau!. It is a seaside Gym with a rectangular battling field having two raised platforms on the opposite ends. Cameron challenged Marlon for a Gym battle and won, earning himself the Wave Badge, thus completing his collection of eight Badges required to participate in the Unova League.
Pokémon used in Gym
Jellicent was the first Pokémon Marlon used against Cameron in their Gym battle. He battled Cameron's Ferrothorn, and after being defeated by Ferrothorn's Thunderbolt, his Ability activated, disabling the move.
Mantine is Marlon's ace Pokémon. It was the second Pokémon Marlon used against Cameron in their Gym battle. It quickly knocked out Ferrothorn with a combination of Wing Attack, Bullet Seed, and Psybeam. Afterwards, Mantine faced Cameron's Samurott and was knocked out without landing a single attack on her.