What is the name of the gear ability that increases swim speed?

The gear ability that increases swim speed is Swim Speed Up.

In Splatoon 2, gear abilities are passive bonuses attached to headgear, clothing, and shoes. Swim Speed Up improves how quickly an Inkling or Octoling moves while swimming through their own ink, making it useful for rotating between positions, escaping danger, and reaching objectives faster.

It is easy to confuse this ability with Run Speed Up. Run Speed Up affects movement in humanoid form, while Swim Speed Up applies specifically to squid or octopus form. Ink Resistance is a defensive ability that reduces the effects of walking through opponents’ ink, and Quick Respawn reduces recovery time after being splatted; neither one directly improves swimming speed.

The ability is especially valuable in modes where rapid movement matters, including Turf War and objective-based Ranked Battles. Its benefit is tied to ink swimming rather than ordinary movement, so players generally combine it with gear or weapons that help maintain access to their team’s ink.