Soviet Installation - Ancient Cistern Challenge Tomb (Part 5)

Carry the can into the side room.

Go up the steps and around to the end of the ledge closest to the wooden door.

Toss the can onto the doorsill.

Then shoot the can to destroy the door, raising the water level to its highest point.

Swim through the opening where the wooden door was to get back to the main room.

If you missed document #7 or the Archivist Map earlier, you can swim across to the alcoves on the northwest side of the pool to get them, along with a few Byzantine coins and some cloth.

Finally, swim across to the dome. Pick up some salvage and cloth, then examine the codex to automatically learn a new skill: Natural Instincts. This reveals the location of nearby crafting resources on your map and glow when you approach them.

When you're ready to go, swim back to the passageway in the northeast corner and follow it back to the Cistern Cavern Base Camp. From there, you can fast travel to any other camp or continue along the passage to climb out the way you came in.