You must solve another environmental riddle. After getting Lara out of a flooded tunnel, you will find yourself in a large room with the tomb. Once again, you must raise the water level to get to the upper parts of the chamber. Walk below, jump into the water and notice that on the right side there's another fragment of unstable wall. If you do not see it, help yourself with Lara's instinct by pressing the right analog stick. Walk to the pointed location and use the axe. After three hits, water will flow from the hole and the water level in the chamber will rise.
Swim to the other side, near the rock ledges shown on the picture above. Start climbing on them. Get to the top, move right, pull yourself up. A platform is hanging on ropes ahead of you. Jump towards it. Lara will hang on the wooden platform and the weight will open the sluice. Water level will rise once again and Lara will fall from the platform. Swim towards the beams painted in white and attached to the wall. Climb on them, move as far right as possible (behind the corner) and, once you have the corridor on the floor ahead of you, pull up to it.
After walking few steps, the floor under Lara will collapse. During such moments (there are more of them), the game will test your reflexes. The time will slow down for a second and you must quickly jump to avoid falling into a spike trap.
Jump to the other side of the chamber using the destroyed pillars and enter the dark corridor leading right. Watch out! After another dozen of steps the floor under Lara will collapse once more - when the time will stop, jump ahead. A moment later a trap will activate in the ceiling. The time will slow again and you must shoot two weak points of the trap before the girl is killed by a sharp object.
Another environmental riddle is the last in this location. Shoot the weak point of the hanging wooden platform shown on the picture above. The platform will fall to the water below. Now, using the hanging platform (it's also visible on the screen above), jump to the other side - you must do it very quickly, otherwise Lara will be washed from the platform and you will have to repeat the jump. Use the axe to break the wall. Water will start flowing from the hole and the water level in the chamber will rise.
Jump again on the wooden platform and this time let the water wash you off. Quickly swim to the previously shoot platform which now is on the surface, climb on it and from there jump on the part of the wall nearby. Climb the wall, move right and jump to the pillar on the right.
Once you stand on the pillar, notice that above the counterweight a board partially painted in white is hanging. Jump towards it. Lara will be once more washed by the water, allowing you to get close to the tomb. Climb up the wooden ledges with skulls.