Kanohi Kaukau

Kanohi Kaukau, mask of breathing underwater.

This mask is known to be worn by Toa Gali. It is covered by many thousands of small, transparent crystals, absorbing the CO2 in the breath of the wearer. Hereafter, it returns it as oxygen, allowing the wearer to breathe, even underwater. This is pretty much the same process as Photosynthesis which function in plants.