Part 22

When the rail car stops at a lowered barrier arm, exit the car and approach the security guard.

After the guard finishes talking, use the switch on the wall near him to raise the barrier arm.

Nudge the guard until he walks onto the track in front of the rail car.

Get back on the rail car and use it to run over the guard.

Quicksave before moving onto the rail car elevator.

Be aware of four barnacles on the ceiling above the elevator. You may be able to ride the elevator down without being caught, or you may need to quickrestore and try again, possibly changing your position on the rail car.

If you continue to be caught by barnacle tongues, move to a position where you can shoot all the barnacles before riding the elevator.

At the bottom, ride the rail car forward through electrified water until section c2a2a loads.

As you move forward, you will pass under a place in the ceiling with a headcrab; it will likely move between ceiling parts and can be ignored.

After going up a ramp and leaving the electrified water, you can choose to abandon the rail car and proceed on foot, though this is not the optimal path.

Shortly after the rail car turns right, you will reach a small wooden platform on the right with an armor battery. You can stop the car to collect it if needed.

To collect the armor battery, get onto the platform and bash it with the crowbar. After falling into the water, swim back to use a ladder to climb onto the area where the houndeyes are located.

Move past the armor battery and stop the rail car, then put it in reverse.

Back up to a side area containing three houndeyes.

Quickly kill the houndeyes with the assault rifle.

Park the rail car next to their floor, ensuring it does not block the red ladder leading down into the water.

If you choose to explore the water, use the flashlight to see and locate the entrance to an underwater tunnel (crouch to approach).

The underwater tunnel leads to a location where you can obtain bullets next to a dead security guard.

To avoid drowning and leeches, drop into the water past the front of the rail car and keep your head above water as much as possible. Move quickly underwater and only stop to deal with leeches if they are about to run into you.

After collecting the bullets, return the way you came and climb the ladder to the houndeyes' floor.

Enter the nearby corridor and proceed to section c2a2b2, an optional area containing useful items including your first C4 satchel bomb.

In the large side room to the left, a bullsquid is present. You can sneak-shoot it with a pistol.

Alternatively, to engage the bullsquid differently, equip the assault rifle, enter the room until the bullsquid sees you, then immediately run back down the hallway to a room with three houndeyes.

Use the assault rifle to spray the houndeyes and interrupt their charge-ups.

After the houndeyes are dead, return to the hallway to find the initial bullsquid fighting another bullsquid that has appeared.

Shoot the remaining bullsquid until it dies.

Look into the watery area next to the houndeyes' room to find another bullsquid. Shoot the explosive barrels nearby if possible, then kill the bullsquid.

Return to the large side room and search near the bodies for ammo clips if you used many bullets.

To find shotgun ammo, approach the large red "BLAST DANGER" doors at the back of the room and open them.

Crouch and move forward until you see a marine's feet on the other side of a rocket. Do not shoot the marine.

Wait for the marine to be attacked by headcrabs.

Finish off any surviving marine(s) with the pistol.

Run back through the blast doors and grab the marine's shotgun.

Immediately run back through the blast doors to avoid headcrabs that drop down nearby.

Return to where you shot a bullsquid in the water.

Use the switch on the wall near the watery room to extend a bridge over it.

If you do not have five tripmines, drop into the water; one tripmine is located near the green crate.

After obtaining the tripmine, jump-crouch onto the crate, then perform a running jump-crouch to the nearest wall ledge.

Crouch quickly after jumping to avoid being zapped by the dangling electrical cable.

Turn left and hop onto a higher piece of concrete, then move onto the bridge.

Kill the two barnacles in the room past the bridge with the crowbar.

Use the .357 Magnum to sneak-shoot.