Marill is a small blue mouse-like Pokémon. It has a round body and round ears. On the top of its tail is a small blue ball.
Gold/LeafGreen/HeartGold Pokedex Description: The tip of its tail, which contains oil that is lighter than water, lets it swim without drowning.
Silver/FireRed/SoulSilver Pokedex Description: The end of its tail serves as a buoy that keeps it from drowning, even in a vicious current.
Crystal/X Pokedex Description: The fur on its body naturally repels water. It can stay dry, even when it plays in the water.
Ruby/Omega Ruby Pokedex Description: Marill's oil-filled tail acts much like a life preserver. If you see just its tail bobbing on the water's surface, it's a sure indication that this Pokémon is diving beneath the water to feed on aquatic plants.
Sapphire/Alpha Sapphire Pokedex Description: When fishing for food at the edge of a fast-running stream, Marill wraps its tail around the trunk of a tree. This Pokémon's tail is flexible and configured to stretch.
Emerald Pokedex Description: Its body is covered with water-repellent fur. Because of the fur, it can swim through water at high speed without being slowed by the water's resistance.
Diamond Pokedex Description: Using its tail as a float, it dives underwater. It likes eating plants that grow on river bottoms.
Pearl/Y Pokedex Description: The tip of its tail is filled with oil that is lighter than water, so it acts as a float.
Platinum/Black/White/Black 2/White 2 Pokedex Description: The oil-filled end of its tail floats on water. It keeps Marill from drowning even in a strong current.
Pokemon (C) Nintendo, GAMEFREAK, Creatures