Part 35

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

Cross the adjacent room to shut off the "surgical unit".

Warning: Run and jump across the left side of the room when it looks safe.

Use the sparking control panel to shut off the surgical unit. 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 any scientist to get him to follow you.

Exit the surgery room, turn left, and lead the scientist through the hallway with broken-open headcrab cages. He may stop following; talk to him again if needed.

Go past the cages back to the lobby.

Check the lobby's side hallway for a marine and attack him with the assault rifle if present.

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

Use a nearby HEV station if needed.

Go through the doors and the turnstile to reach section c2a4g.

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

Sneak-shoot the nearby marine with the .357.

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

Get out your pistol and slowly move back to see the top of a turret. Shoot it down.

Move back to see the other turret and shoot it down.

Shoot the explosive crates blocking the path ahead.

Go past them to find crates with armor batteries and .357 ammo.

Go 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.

Marines are hiding around both corners ahead; use the pistol to sneak-shoot them.

Get out the assault rifle and go down the central path to see more marines. Fire an AR grenade at them, then back up and shoot them as they appear. Alternatively, shoot explosive barrels first, or use the crossbow to sneak-shoot the first marine, or toss five snarks before they see you.

Check for health packs and return to where the last two marines were if your armor is less than 100%.

You will find yourself near a small dam with a sandbag-protected mounted gun at the other end.

When you approach the dam and hear the Apache helicopter, quickly shoot at the sandbag-protected gun with the assault rifle until it blows up. The assault rifle bounces a lot; consider using the pistol or a fully powered alt-fire blast from the gauss gun.

As soon as the gun emplacement is blown up, turn left and run for cover (press the cover button to crouch behind walls or objects) in the nearby dark corner to avoid the chopper.

Stay in the dark corner; the chopper will fly back and forth, shooting at the ichthyosaur in the water.

Wait for the chopper to kill the ichthyosaur. Periodically quicksave, run for the water, and quickrestore if the ichthyosaur is still alive. You can finish it off with the shotgun and/or assault rifle if impatient; stay in the corner where you drop into the water to avoid being chomped.

Before dropping into the water, you can destroy the chopper with two fully powered alt-fire blasts from the gauss gun. One blast is sufficient.

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

Climb the ladder on the side of the tower.

Inside the tower's room, use the first aid station if needed.

Use the big button panel to turn its button red.

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