Hydro Dweevil

The Hydro Dweevil, called the Caustic Dweevil in the GameCube and Wii versions of Pikmin 2, is an enemy in and. A non-aggressive member of the dweevil family, it picks up any treasure or enemy corpse it can find, only releasing it when Pikmin interfere, at which point it will attack them by spraying water, which suffocates and drowns all Pikmin types except Blue Pikmin, Bulbmin and Glow Pikmin, making those the best choice in battle against it.

Behavior
Hydro Dweevils scurry about randomly and take no note of the presence of any leader or Pikmin if left undisturbed. When provoked one will attempt to defend itself by releasing a pressurized spurt of water below it. Hydro Dweevils are frail creatures and will die quickly if attacked by even a few Pikmin, or by the punches from a leader.

When a treasure or a corpse of another creature is nearby, a Hydro Dweevil will lift it up onto its head and carry it, making it impossible for Pikmin to collect until it is broken free. When a Dweevil has an item in its possession, it will stay at rest, crouching down, appearing as if it is only the item, until it is approached by a leader or Pikmin, at which point it will stand up and run away.

Strategy
Throw any type of Pikmin onto a Hydro Dweevil's small head. Although they can harm non-Blue Pikmin, they are weak and often die before getting a chance to attack at all, and this does not kill Pikmin instantly, allowing them to be whistled to safety by a leader if they do come into contact with the attack. Be aware, however, that depletion of a Dweevil's HP will not stop an oncoming attack, so if one starts its attack animation, be prepared to whistle your Pikmin back. Purple Pikmin are particularly useful in defeating large numbers of smaller Dweevils with ease, since they stun when thrown, halting any enemy attacks, usually until death. Also to be advised is that the Hydro Dweevil can stun leaders regardless of what upgrades they have, this can put suffering Pikmin in danger of dying as the stun will prevent whistling while active.

Alternatively, you can use leaders to defeat the creature in an ultimately safer way. Run up to it and punch it until it begins its attacking animation, leaving plenty of time to run away before it attacks. Run back and continue the assault when the water flow stops.

Trivia

 * The Hydro Dweevil was planned to be included on the 2-Player Battle Roulette Wheel as an enemy, but was eventually removed. It's paired up with the Fiery Dweevil, and it shares its removal with the Spotty Bulbear and the Antenna Beetle.