Water Compaction (Japanese: みずがため Water Fortifying) is an Ability introduced in Generation VII. It is the signature Ability of Sandygast and Palossand.
When a Pokémon with Water Compaction is hit by a Water-type move, its Defense rises by two stages. It will activate for every hit of Water Shuriken.
It is unknown if Water Compaction has any effect outside of battle.