Kuwaq Yaku – First Crypt (part 1)

Crack open the nearby salvage crate, then enter the flooded cave and dive below the surface.

Swim through the tunnel until you can surface for air.

There are a few plants you can gather underwater and a vein of gold ore on the right (north) wall of the pool.

Climb out of the water on the left and follow the tunnel. (There's more gold ore on the ledge with the skeleton to the right. You can get it by following the tunnel around behind it, or wait and retrieve it on the way out.)

A little farther on, your progress is blocked by a flammable barrier. You can burn it away with a fire arrow, or use one of the glass bottles and cloth found here...

...to craft a Molotov and throw it at the barrier.

Enter the room beyond and look to the left to find an archivist map (2/3) sitting on a stack of plastic pipes. Examine it to reveal several documents and murals on your map.

Continue through the next room to find a mural (2/10), Wayta, the Tyrant (Quechua/Resting Places).

Proceed to the southwest. When Lara steps out onto the rickety wooden ledge overlooking the slope and deep pit beyond...

...the ledge collapses and she starts to slide. Steer to the right...

...left...

...then right again to avoid being impaled on the spiked walls.

Then just before you reach the edge of the large pit, press Jump then Interact...

...to grapple-swing across the gap.

Continue forward, jumping across a smaller gap...

...to the room with the sarcophagus. Open it to obtain an outfit component, Vestige: Nine Strides' Boots, plus 750 gold pieces. Once you restore and equip the boots at a base camp, they'll allow you to harvest more man-made resources from each source.