What it does
Waterfall is a Water-type physical move with 100% accuracy and a flinch chance on hit. Super effective against Fire, Rock, and Ground — all common types in the Champions field. The flinch doesn't trigger often enough to plan around, but it occasionally creates an extra free action for your partner when it lands.
Who runs it
Gyarados runs Waterfall in 98% of sets. With 125 base Attack and Mega Evolution available in Champions format, this is its primary damage slot. The move is simple and does its job: reliable Water-type physical damage with no accuracy issues. Under Rain, Water moves get ×1.5, which pushes Waterfall into territory very few things comfortably absorb.
How to use it
The decision is easy: target has a Water weakness, or you need physical damage and nothing else is sharper. 100% accuracy matters in games where a miss on turn 5 costs you the match. In doubles, no spread penalty applies — you're putting the full amount into whoever you're targeting. Gyarados's attack stat combined with a super effective hit tends to KO or leave opponents at very low HP, which sets up the next turn favorably.
Tips & strategy
Electric is a ×4 weakness on Gyarados, and no amount of Waterfall power changes that. The plan is to click Waterfall freely in turns where Electric coverage isn't threatening you, and manage the Electric matchup through positioning and partner support. Under Rain, the damage output is high enough that most opponents need to treat it as a direct threat. The flinch chance is real upside when it fires — just don't factor it into your damage calculations when deciding whether to go for a KO.