Following the storyline in Shadow of the Tomb Raider you will find yourself in a small location called Cenote. There you will be able to complete two challenges.
The sunken treasure challenge consists in open several crates underwater. The area that relates to the challenge has been marked on the screen above. This will make it easier for you to find all the chests.
In underwater of the Cenote location you will find 5 sunken chests. To open them you need your axe. From each box you will get raw materials and experience points.
To complete the Sunken treasure challenge you must open 5 sunken crates. When you open each of them the challenge will be completed.
To start the Respected challenge you must go to the area marked on the map above.
The Respected challenge consists in the destruction of several figures in the Cenote location. They are fixed to trees. In order to destroy them you have to shoot from the bow in the rope under the statue. This way Lara will pull the rope and damage the figure.
To complete the challenge you have to destroy 5 figures. When you do this the challenge will be completed.