What it does
Every Water-type move hits 20% harder. No HP cost, no lock-in, no trade-off beyond non-Water coverage moves getting nothing. That's the whole deal.
Who runs it
Palafin at 78% is the clearest endorsement. Its offense is concentrated almost entirely on Jet Punch, a priority Water move it spams every game. No coverage needs, no lock risk — Mystic Water is perfect. Primarina at 32% follows similar logic: Water is its primary STAB, and the freedom to use Moonblast when needed without penalty is worth more than a 10% damage bump from Life Orb. Blastoise at 28% is slow but bulky, and recoil chips away at the staying power it depends on.
On rain teams, the real multiplier is stacking: rain already applies ×1.5 to Water moves, and Mystic Water's ×1.2 on top brings the effective multiplier to ×1.8. The setters (Pelipper, Politoed) don't need it — the Water attackers launching off that platform do.
How to use it
Turn 1, get rain up. Turn 2 onward, Water attacks are running at ×1.8 effective multiplier without the HP drain of Life Orb. That longevity matters — especially for Palafin which often needs to hit priority moves multiple times in a single game.
Plan around non-Water moves getting zero benefit. If Palafin needs Close Combat to handle a Steel type, that move runs on raw Attack stat alone.
Tips & strategy
Mystic Water vs Life Orb: ×1.2 vs ×1.3. Life Orb is a stronger single hit, but four attacks costs 40% total HP — effectively donating a KO to your opponent. For priority-move users like Palafin that fire off five or six attacks per game, Mystic Water's survivability advantage compounds fast.
Mystic Water vs Choice Specs/Choice Band: Choice items multiply by ×1.5 and are numerically stronger. But locking into one move against a savvy opponent lets them freely swap in an immunity or resist. In doubles especially, Mystic Water's flexibility is worth more than raw power.