Part 29

Leave the underwater passages by going straight and then turning right.

In the next room, an ichthyosaur will eat a scientist. You can kill it from the side of the pool, but it's time-consuming and ammo-intensive.

Carefully move around the room, avoiding slick spots and barnacle tongues.

At the end of the walkway, enter a side area with a ladder leading to a room with a scientist, first aid station, and HEV station.

Continue past the stations and along a metal beam to a spot where you can drop into a hanging cage to grab the crossbow. Quicksave before doing this.

Maneuver in the cage until it falls into the water. Swim up through the gap and turn left towards the underwater doorway. Swim quickly to avoid the ichthyosaur. If you are bitten, keep going to the scientist's room for healing, or quickrestore if bitten multiple times.

Alternatively, to get the crossbow, drop onto the top edge of the cage and slowly crouch-walk forward to grab it as you fall into the water. The underwater doorway is ahead and to the left.

Return to the walkway and go back to the entrance of the side area with the ladder.

Look for a door next to a broken-off walkway at the back of the ichthyosaur tank.

Get out your crowbar and run-hop along the water to a barnacle whose tongue hangs near the end of the broken-off walkway.

When caught by the barnacle, look up and attack it. Lean on the "Move forward" key to land on the walkway.

Go through the door, then the doorway on the left, and down steps to an underwater area with two crossbow clips. Collect them.

Return the way you came and continue down the corridor until section c2a3b loads.

In the underwater gate section, dive into the water and go to the corner left of the broken-off walkway. Find the gate and its red wheel.

Surface for air, then dive back down and use the wheel until the gate is mostly raised. Swim under it and along the passage to surface for air.

Return to ensure you collected all crossbow ammo near the gate.

In the Two-Ichthyosaur Tank and Generator Piston Room (section c2a3b), go up steps and through a door into a room full of barnacles.

Stay near the door and kill all barnacles with the shotgun.

Shoot the top of the large crate with shotgun shells on it to make two vortigaunts teleport in. Retreat past the door for cover (press the cover button to crouch behind walls or objects).

Shoot the vortigaunt on the walkway, then sneak to the floor below and shoot the other vortigaunt.

Go to the floor and bash crates for shotgun ammo.

Move down the hallway to the next room with a broken walkway and two ichthyosaurs.

Go to the end of the first walkway segment, turn left, and look for a hole in the fencing in the back corner. Quicksave.

Run-hop along the water surface and jump through the fence hole. Quicksave or quickrestore if you miss and the ichthyosaurs get you. Jump-crouching might help.

As soon as you are past the fence hole, dive down and swim quickly along the underwater passage to a ladder.

Climb the ladder to a large room, then run down the side passage ahead and to the left.

Climb the next ladder to the upper floor. A bullsquid may have followed you; if not visible, backtrack and sneak-shoot it with the crossbow.

Return to the upper floor. Crossbow-kill the second bullsquid that teleports into the lower floor.

Go down the passage at the other end of the upper floor to find a side room with ammo.

Follow the walkway past the side room to find another crossbow clip.

Return to the upper floor of the big room.

Push the small metal box so it falls to the floor below, then drop after it.

Push the box against the large green crate in the back left corner.

Jump onto the metal box and then jump-crouch onto the green crate.