Part 35

Drop down to the floor, go up steps, and through a door to a small room with three scientists.

Enter the adjacent room and shut off the "surgical unit" by using the sparking control panel. If it blocks the walkway, turn it on and off again until clear.

Use the blinky-light panel to the right of the doors to open them.

Talk to one of the scientists to get him to follow you.

Exit the surgery room, turn left, and lead the scientist through the hallway with broken-open headcrab cages. If he stops following, talk to him again.

Go past the cages back to the lobby.

Check the lobby's side hallway for a marine and engage if present.

Approach the retinal scanner to the right of the lobby's exit doors and wait for the scientist to unlock them.

Use the nearby HEV station if needed, then go through the doors and the turnstile to reach section c2a4g.

As the outer doors open, crouch-walk through and stay near them as they close.

Quickly shoot a nearby marine with the .357.

Go to where the dead scientists are, turn around, and look up at the top of the nearby wall.

Shoot down the two turrets from a distance using the pistol.

Turn and shoot the explosive crates blocking the path ahead.

Go past the crates to find more crates containing armor batteries and .357 ammo.

Proceed to the big door to start the "Surface Tension" chapter.

Use the button panel to the right of the door to open it and run through before it closes.

Deal with marines hiding around the corners ahead using the pistol.

Use the assault rifle to engage more marines down the central path, potentially using an AR grenade or shooting explosive barrels first.

Check for health packs and return to the armor battery location if your armor is less than 100%.

Return to where the last two marines were to find yourself near a small dam.

Take out the sandbag-protected mounted gun at the other end of the dam.

As the Apache helicopter starts, shoot the mounted gun with the assault rifle until it blows up.

If the chopper attacks, duck for cover.

Wait in a dark corner for the chopper to engage the ichthyosaur in the water.

Periodically quicksave and check if the ichthyosaur is dead; quickrestore and wait if it's still alive. (Alternatively, finish off the ichthyosaur with the shotgun/assault rifle while staying in cover.)

Optionally, destroy the chopper with two fully powered gauss gun altfire blasts before entering the water.

Dive into the water next to the dam and swim to the small tower structure.

Climb the ladder on the tower's side.

Inside the tower, use the first aid station if needed, then use the button panel to turn its button red.

Quicksave, then dive into the water and locate the valve wheel on the dam wall near a red light.