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A marsh tile is a special tile introduced in Pokémon Diamond and Pearl. When the player walks on these tiles, they may become stuck in an unseen hole and unable to move.
Marsh tiles are found on Route 212, inside the Great Marsh, and in the Johto Safari Zone in Generation IV. In Pokémon X and Y, these tiles can be found on Route 14 and Route 19.
In Generation IV, wild Pokémon cannot be encountered in most marshy areas. Inside the Great Marsh and the Johto Safari Zone, however, tall grass grows on some of the marsh tiles, allowing for wild Pokémon battles.
In Pokémon Diamond and Pearl, the holes a player may get stuck in are scattered among and indistinguishable from safe marsh tiles. In Pokémon Platinum, the difference in depth between a safe marsh tile and a deeper hole is explicitly visible, and the deeper tiles are concentrated together in clusters. In all three games, to get free from a hole, the player must struggle free from the marsh by pressing different directions on the D-Pad.
While the player cannot ride their Bicycle on marsh tiles, they can freely run on safe marsh tiles.
The Hole trap used in the Underground works similarly to the marsh tile's holes.
In Generation VI, wild Pokémon can be found in all marsh tiles.
Marsh tiles come in two degrees of depth. In both the shallow and the deep marsh tiles, the player can run, skate, or bike, but in the deeper tiles they will be slowed down to nearly walking speed. Both depths may contain unseen holes, though they are more common in the deeper tiles. When the player falls into a hole, they will automatically pop back up out of the hole after a short time. If the player was biking or skating when they fell into a hole, they will instead be walking when they extract themselves.