Continuity mistake: When Lara first arrives on the boat, she removes charts, etc from a waterproof bag (it has a black plastic seal with yellow screws). Yet when she dives she appears to have only her standard Lara Croft-style backpack, which would not stand the pressure, even if it was waterproof. Further to this, when she escapes the Temple, she no longer has it, yet her headset and video camera survive the pressure and submersion of her shark ride and subsequent 3 days in the water.
Continuity mistake: When Lara and Terry escape from the Shay-Ling on the ropes,upon reaching down they make a very unrealistic turn. They climb down heads first, and they flip so as to fall on their feet on the ground. But the motion is very "robotic". Even if they were very strong athletes, this would still be impossible, as the rope should be very stretched (should be fixed at both ends). Otherwise, it would not give them the support they need for such a flip. All the way down you can see that, at the bottom, the ropes go through some sort of pulley system. It is only after Lara and Terry are standing on the ground that the ends are shown swinging freely. So their dismount is realistic in one version of the scene, but unrealistic in another.
Continuity mistake: When Lara is looking at her guns and knives in the old Chinese lady's house, you can see that Lara's hair is at least six inches shorter than at any other time in the movie.
Continuity mistake: When Lara is sliding down the rope, she fires at the guards at the top. However, when the action cycles, the shell would not clear the port before the slide came forward. Therefore she should have only fired one shot, then have a blockage.
Answer: The pressure in the temple would be the same as that of the water just before Lara entered the temple. So no she would not need to decompress before entering at the temple as it was open to the sea, but she would have surely suffered the bends on the rapid accent to the surface.