Water Wave

Water Wave (ウォーターウェーブ) is Wave Man's Special Weapon in the Mega Man series. The weapon uses high pressure to inject compressed water in one direction with enough power to pierce through steel. When used by Mega Man, he sends out three water spouts as a small wave across the floor that can absorb some enemy projectiles. The waves can only be fired when Mega Man is in contact with the ground. It will stop when it hits an enemy that is strong enough to sustain the hit, or until it hits a wall. It cannot be activated while Mega Man is in the air or on a levitating platform. It also can't be activated if Mega Man is at the very end of a ledge. However, it can be activated on a ledge provided it has time to flow off the edge where it will fall to the ground, and continue to travel until it hits something in its path.

Mega Man 5
Mega Man obtains Water Wave after defeating Wave Man. One Water Wave uses two weapon energy units. With a full weapon energy gauge, Mega Man can use Water Wave fourteen times.

Water Wave is Star Man's weakness. Not only does it inflict four units of damage against him, it also negates any Star Crashes he creates. It is also effective against Dark Man 1, inflicting three units of damage against it.

Damage Data Chart
Damage values in units in Mega Man 5.

Mega Man (Ruby-Spears)
Mega Man used Water Wave in the episode 20,000 Leaks under the Sea of the Mega Man animated series. Used exclusively underwater, it takes the form of a churning funnel of water which is able to deflect enemies and some projectile attacks.

Mega Man (Archie Comics)
In the Worlds Collide crossover, Wave Man attempted to use Water Wave on Sonic the Hedgehog, but Sonic avoided the attack with his speed.

Mega Man Megamix
Wave Man's Water Wave forces highly pressurized water into the ground, which travels through underground channels, pipes, and sewer lines to erupt elsewhere as a pillar of rushing water. This attack is based on Pascal's Law, which states that when pressure is applied to a contained liquid, its volume remains uncompressed while the pressure is conveyed undiminished throughout the liquid and to the surface of its container. When the Fifth Numbers attack together, Wave Man is the second to attack, using Water Wave to push the target to Crystal Man.

Other appearances
Water Wave appeared in the Rockman 5 manga and in Rockman 4Koma Dai Koushin.

Trivia

 * Water Wave, Rush and Super Arrow are the only items affected by the gravity of Gravity Man's stage. While upside down, Mega Man is unable to use New Rush Coil and Rush Jet, he can't stand on Super Arrow, and the Water Wave only works if it is used at the time he touches the floor (or any terrain above Mega Man when he is on the ceiling).