Water Gun is the move Pokémon Pokopia uses for watering dry plants.
Pokopia turns familiar Pokémon moves into practical tools for restoring the environment. The official game description gives Water Gun as an example: Ditto can learn it from Squirtle and use it to refresh thirsty plants.
This system differs from the battle-focused use of moves in the main Pokémon games. In Pokopia, befriended Pokémon teach the player new abilities, and those abilities help alter the world. Other tasks include creating bushes, cutting debris, and smashing rocks.
Water Gun is sometimes confused with Surf because both are Water-type moves associated with water. In Pokopia, however, the specific gardening example is Water Gun. The move's role demonstrates how the game connects Pokémon abilities to crafting, cultivation, and habitat restoration.