Hydruka were a breed of sea Rahi which the Matoran of Mahri Nui used to harvest air bubbles from the fields of air. Hydruka were able to sense which stalks of airweed contained the most air. They were notoriously stubborn and ill-tempered. They defended themselves by launching solid air spheres at enemies.
Hydruka were scorpion-like sea creatures. They were domesticated beasts used by the Matoran of Mahri Nui to harvest air bubbles from airweed. Their means of defense, launching air bubbles at enemies, inspired the Matoran to build their own launchers for the defense of their city. Hydruka were notoriously sensitive, stubborn, and temperamental. They worked at their own pace, and attempting to rush them only frightened or angered them.