The Kaukau Nuva was the Kanohi Nuva Mask of Water Breathing, formed when a destined Kanohi Kaukau was exposed to Energized Protodermis and transformed. The Kaukau Nuva gave its user and those nearby the power to breathe underwater for an indefinite amount of time, even at extreme depths. The Kaukau Nuva's power could have been used to suffocate opponents via sharing its power, but Toa considered that to be an immoral application. The only beings able to activate this mask's power were Toa Nuva.