Part 22

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

Use the switch near him to raise the barrier arm (or he will do it for you).

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

Get back on the rail car and run him over.

Quicksave before approaching the rail car elevator.

Be aware of four barnacles on the ceiling above the elevator.

You can likely ride the elevator down without being caught by a barnacle tongue.

If caught, Quickrestore and try again, possibly changing your position on the rail car.

If you continue to be caught, shoot all barnacles before riding the elevator.

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

As you proceed, you will pass under a ceiling section with a headcrab; it will likely move and can be ignored.

After ascending a ramp and leaving the electrified water, you can abandon the rail car for the remainder of the chapter, though this is not the optimal path.

Soon after the car turns right, you will reach a small wooden platform on the right containing an armor battery.

Stop the rail car next to the platform to collect the armor if needed.

To get the armor battery, get onto the platform, bash it with the crowbar, and collect it after falling into the water.

Swim back to use a ladder to climb onto the area with the houndeyes.

Continue around the corner past the battery, then stop the car and reverse.

Back up to a side area with three houndeyes; kill them quickly 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.

To find an underwater tunnel entrance, drop into the water, use your flashlight, and crouch as you approach.

The tunnel leads to 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.

If you must go underwater, move quickly and only stop to deal with leeches if they are about to hit you.

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

Enter the nearby corridor to reach section c2a2b2, an optional area containing the C4 satchel bomb.

In the large side room to the left, a bullsquid is present.

You can sneak-shoot the bullsquid with the pistol, or lure it out.

To lure it, get the assault rifle, enter the room until the bullsquid sees you, then run back to the end of the hallway.

In the hallway, find a room with three houndeyes; kill them with the assault rifle, interrupting their charge-ups.

Return to the hallway to find the first bullsquid fighting a second one that appeared.

Kill both bullsquids.

Look into the watery area next to the houndeyes' room to find another bullsquid.

Shoot any explosive barrels near it, then finish it off.

Search near the bodies in the big side room 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 on the other side of a rocket.

Do not shoot the marine; wait for headcrabs to attack him.

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

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

Avoid the headcrabs that drop down by immediately running back through the blast doors.

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 is located near the green crate.

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 electrical cable.

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

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

Use the .357 to sneak-shoot the next target.