The Kanohi Kaukau Nuva was the more powerful version of the Kaukau. In addition to allowing underwater respiration, it allowed its user to stay under longer and to breathe at greater depths. As with all Kanohi Nuva, its power could be shared with those in close proximity.
Gali's Kaukau Nuva allowed her to plunge to the very bottom of the sea and survive. The Great Mask of Water [sic]. It allowed the user to breathe underwater for an unlimited time, even at extreme depths.
The Kanohi Kaukau Nuva was the Great Mask of Water Breathing. It allowed its user to breathe underwater.