Cenote – Flooded Cavern

When you're ready to move on from the pool below the Cenote Vista Base Camp, swim through ths square doorway to the west.

Follow the natural passageway forward, crack open a salvage crate along the way, and continue to a pocket of trapped air.

Use this as a base to get the various pickups nearby. Start by taking a breath then swimming back to the east and downward through the opening in the floor...

...to find some healing plants...

...a resource canister, and some jade embedded in the wall near the canister. There's also a second air pocket in this lower passageway to the west. Use it if you need it. Then return to the first air pocket, in the passageway above. (It's marked on the map in case you get disoriented.)

Once again swim back to the east. This time, swim past the opening in the floor and the ledge with the broken wagon where you found the salvage earlier.

Swim down the slope and around to the right...

...to find a survival cache (3/8) buried on the cavern bottom. It will be marked on your in-game map if you found the explorer backpack earlier. Dig up the cache.

Then return to the first air pocket.

Take a breath then swim down to the left (south) to find a relic (2/5), Knight's Morion (Gates of Hell).

Surface here...

...in a small cave with some jade and a minor mural containing information about the Box. As Lara is examining the mural, something creepy and human-shaped moves behind her, casting a shadow across the mural.

Jump back in the water and swim through the tunnel to the right to find another resource canister.

Then continue around to the left to get back to the first air pocket.

Take a breath and continue forward (west) into the next flooded cave. Turn right at the huge, carved skull.

Swim into a side tunnel then straight up to the surface.

Climb out of the water on a ledge with some jade and a document (2/6), A Warning (Gates of Hell).

Now, if you don't care about getting 100% completion, swim out of this creepy cave, drop all of your gear, charter a plane, and head back to England immediately!!! Not an option, you say? All right. In that case, swim down out of the side area where you found the document. Approach the giant stone skull, turn right (west), loot another resource container, and follow the tunnel to a larger cavern, where you can climb out of the water.