Using this technique, Haku gathers some water from the air and surrounding environment into one thousand long needles. He then directs them to a specific target at high speed, leaping backwards before impact so he doesn't get caught in the crossfire. While the needles do surround a target from all sides, they don't appear above the target, creating an escape route. Haku is able to perform this jutsu with one-handed seals, allowing him to pin an opponent's arm and attack while they cannot use any techniques themselves.
In the manga and anime, Haku calls this technique by its full name, Secret Technique: Thousand Flying Water Needles of Death (秘術・千殺水翔, Hijutsu: Sensatsu Suishō). The databook entry for this technique drops the "Secret Technique" part.