Part 15

From the start, jump-crouch onto a hatch and crouch-walk onto a pipe. Jump to the next pipe on the same level. Run along the pipe to a turn, then jump to a railed platform to avoid bullsquid spit.

If needed, pick up health packs and armor batteries from a table. Proceed to a large room with toxic green water.

To cross the toxic water room quickly: get on the long pipe crossing the room, jump to the slanty pipe, then onto the machine next to the lift. Jump onto the lift and crouch-walk to its button panel to activate it. Stay crouched until section c1a4b loads to avoid spit.

(Optional Secret Area) To access health packs and armor batteries on a small table: kill both bullsquids, then get on the lift. Face the button panel, turn right, and look for the table. Move along the rounded, slanty surface connecting the table's ledge to the machine next to the lift. While moving, face away from the water and lean forward while strafing towards the table. For the return trip, aim for the long pipe instead of the machine.

After the lift stops in section c1a4b, crouch-walk forward until you see a bullsquid. Shoot the explosive near it to kill the bullsquid.

Proceed onto the long, curving walkway and kill the houndeyes that approach. Use the shotgun for safety.

Continue along the walkway to a point where you can shoot explosives near another houndeye. This will destroy part of the walkway, creating a gap.

Before jumping the gap, shoot explosives to the right to kill another houndeye. Check the area for health packs.

Shoot the two headcrabs on the other side of the gap while positioned to avoid spit from a distant bullsquid.

You can shoot the distant bullsquid now, but a better opportunity will arise later. Quicksave.

Take a running jump across the walkway gap and enter the small room with a big red switch. Use the switch to proceed to section c1a4i.

In section c1a4i, as the door opens, double-barrel the zombie behind it.

After encountering a dying scientist, look for a barnacle tongue hanging down.

(Optional Secret Area) To access a secret area with first aid and HEV stations: move into the barnacle tongue while passing the scientist, then lean backward immediately after hitting the barnacle with the crowbar. Quicksave before attempting this.

To avoid health damage when leaving the secret area: jump to the wall corner past the barnacle and hold forward. If you don't slide down, tap forward repeatedly until you drop onto the walkway.

Move on and use the red switch next to the next door to open it. This leads to the rocket firing control room.

Observe the three tentacle monsters in the rocket firing chamber grab a scientist. The tentacles will not attack you in the control room.

Leave the control room through the other door. Look up to find and kill a barnacle near a ladder (use your flashlight).

Climb the ladder and enter the room with explosive boxes and hand grenades. A security guard will enter the firing chamber and be killed by the tentacles. Wait for the tentacles to settle.

Crouch-walk through the firing chamber doorway and turn left. Stop near the edge of the platform and look down to see a ladder top blocked by wooden crates.

Quicksave. Toss a grenade to land near the crates and destroy them.

The instant the grenade explodes, crouch-drop off your platform onto the walkway below.

As soon as you land, start crouch-walking in either direction to avoid potential tentacle detection. If detected, they will attack where you landed. If hit, quickrestore.

Wait for the tentacles to settle, then crouch-walk to the top of the ladder.

Quicksave again. Look down at the walkway below to find a boarded-over doorway.

Toss a grenade at the boarded-over doorway, then hurry down the ladder as soon as the grenade explodes.

Crouch-walk away from the ladder in case the tentacles heard you. When safe, crouch-walk through the de-boarded doorway.

Quicksave upon entering the new area.