Aloy has many special pieces of gear that help her explore the west. In Horizon Forbidden West, you can get a grappling hook in the form of the Pullcaster, for example. All of these give you access to different regions and treasures. One of these special items is the Diving Mask, or Rebreather as some call it. This is a game-changer since there are many water regions to be explored.
How to Get the Rebreather in Horizon Forbidden West
You will gain access to the Rebreather during the main quest, “Sea of Sands.” This diving mask is a special piece of gear that allows Aloy to explore underwater without running out of oxygen.
In the quest “Sea of Sands,” you are going to explore the region that once was Las Vegas. This is a big desert, where Aloy meets three men in a tower during part of the main quest. One of them, Morlund, is trying to swim into an ancient chamber with treasures from the past. Then, Aloy offers to help them since this is the same place where Poseidon is located.
Before you can continue with the quest and get the Rebreather, you must collect some items. To get the first item simply dive in the pit full of water from where the men were getting out. You will be looking for the Compressed Air Capsule in a sort of elevator. Once you recover this item, you must hunt down a herd of machines. Use your Focus to track them. There are a considerable number of enemies together, so kill them and loot all to get one Machine Knee Cap and one Synthetic Membrane.
Take all the items back to Morlund and use the workbench to get your diving mask. This is an important item not only for this section of the story but to explore the whole west. Up until now, Aloy would run out of oxygen pretty fast when diving.
However, by having the Rebreather, there is no need to worry about that. Even in more secondary parts of the game, for example, during the process of overriding the Tallnecks, the mask is essential. There are also crafting materials you can only find in the water, so diving is quite important. However, keep in mind that you can’t rush to this area and get the item. It is locked by the story, so keep at it until you reach the “Sea of Sands” quest.