すいすい (Swift Swim)

Swift Swim doubles a Pokémon's Speed stat when rain is active on the battlefield, making it one of the most potent weather-based abilities in competitive play. Crucially, this speed boost does not count as a stat modifier, meaning it cannot be removed by moves like Clear Body or bypassed by abilities that ignore stat changes. The ability activates automatically whenever rain is present, whether from moves like Rain Dance, abilities like Drizzle, or items like Damp Rock extending the weather condition.

This ability transforms naturally slower Water-types into formidable speed threats under the right conditions. Kingdra exemplifies Swift Swim's competitive potential, becoming a devastating special attacker that can outspeed virtually anything in rain while firing off powerful Hydro Pumps and Draco Meteors. Similarly, Basculegion leverages Swift Swim to become a dangerous physical sweeper with Last Respects, while Seismitoad can surprise opponents by suddenly outspeeding them with Earth Power or Hydro Pump.

The tactical implications extend beyond individual Pokémon performance. Swift Swim users often anchor dedicated rain teams, working in tandem with Drizzle setters like Pelipper or Politoed. This creates immediate offensive pressure, as opponents must respect the possibility of a Swift Swim sweep whenever rain is active. The ability's consistency and power make it a cornerstone of weather-based strategies across multiple competitive formats.