The Diving Mask is one of Aloy's most crucial upgrades to exploring underwater caverns and cauldrons. This strange mouth apparatus was teased in promotional materials ahead of the launch of Horizon Forbidden West and led players to believe that Aloy would be able to take the fight under the waves.

　　Without the all-important Diving Mask, Aloy's ability to hold her breath under the waters is reduced to roughly thirty to sixty seconds at a time. The developers at Guerrilla have given Aloy a bit of breathing room, no pun intended, to survive a few extra seconds when her oxygen runs low if the player is making an active effort to surface for air. However, once Aloy gets her hands on the Diving Mask, she's able to stay underwater indefinitely for all of your aquatic spelunking needs. After all, rare Greenshine pieces for upgrading the highest tier of gear can often be found where humans can no longer tread.

　　As with most of Aloy's Special Gear upgrades, the Diving Mask is an essential part of yet another Main Story quest. Depending on which Main Story quest you decide to tackle when the choice opens up, this may be your first of the three choices or the last. Either way, you're going to want to pick up the Main Story quest Sea of Sands which will take you into the dusty desert biome of the Forbidden West.

　　Progressing through Sea of Sands will eventually see Aloy tasked with picking up three components necessary to craft the Diving Mask: Compressed Air Capsule, Machine Knee Cap, and Synthetic Membrane. All three of these materials are marked as key objectives, and the quest markers will be clearly indicated both on the compass and in the environment when Aloy approaches.

　　Once Aloy has all three materials in hand, simply travel to any nearby Workbench and visit the Special Gear crafting menu to create the Diving Mask. As with most of Aloy's Special Gear, you won't have to manually equip or even activate it to work. Just dive into your nearest watering hole and Aloy will now be able to venture to the deepest reaches for loot without any worry about oxygen. Nifty!