Hop into the water and pick up 2 boxes of shotgun shells (40-41) on the way down the submerged stairs. Get air if necessary.
Then swim farther down to find a lever. Pull it...
...to open the gold door in the room above. (This is an exit back to the main area with the TOWER AND HONEYCOMB STRUCTURE. We'll go that way in a little while.)
Roll and swim back to the surface.
Climb out of the water on the ledge near the doorway, where there are 2 switches. Pull the left switch first (left when Lara's back is toward the pool).
This opens the SECOND GOLD DOOR outside in the main area.
NOTE: If you don't care about getting every item and kill, you can leave this area now without releasing the 4 mutants. Pick up the walkthrough with the next section.
If you want it all, pull the switch on the right...
...to release the 4 mutants (22-25). You can then rush out and try and fight them all, but these Atlanteans have fireball and dart attacks, so the block with the switch is no longer safe. It may be easier to take on a few enemies at a time.
Here are a couple of strategies: Pull the switch, press Look to get Lara's perspective back, then quickly jump over the pool to the stairs. The mutants can't cross the water. They will shoot projectiles, though. So climb up to the middle step, directly opposite the door.
From there, you can shoot through the doorway while staying close to the step on the right for cover. If the mutants run away, climb down, jump over to the doorway, then jump back to the stairs and repeat.
- OR -
Alternatively, after releasing the mutants, jump across the pool to the lowest step...
...roll/turn around, and draw the shotgun. Start blasting the mutants as soon as they appear in the doorway. You may be able to kill one or two right away, but the others will probably run off.
Move to the edge of the step, jump over to the doorway to attract the mutants, then backflip onto the step...
...and keep shooting. Lara will suffer some damage from the fire/darts, but close-range shotgun blasts will take out the mutants fairly quickly. Of course, you can also do this with pistols, but you may take more damage.
When all the mutants are dead, go into the cage room.
Pull the switch to open the door at the back of the cage.
Inside you'll find 2 small medi packs (42-43).
DARK MODE: Even with brightness adjusted, dark images on a light background can be hard to see. May I suggest a reputable dark mode browser extension, such as Dark Reader? (Download only from trusted sites, like darkreader.org or your browser's web store.)
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