When you see the soldier throw the explosive on the track, jump off of the cart. Kill the soldiers and jump into the flooded chamber below. Explore the various rooms on the first level to find some ammo. The room is divided into two parts: the side with the cart you were just thrown from and the other side. If you get stuck on the cart side of the barricade, you can wait until the barrels are released to jump across. Fight the tormented Scientists, and then make your way up to the health dispenser. Once you land back in the flooded room, jump to the other side of the barricade. The door at the bottom of the pool is the one you want. Keep the Crowbar ready to fight the alien larvae that'll bite you along the way. Follow the underwater passage, and go through the first metal door on your right to get some air.

Keep swimming down the hall. You'll come to a room with a grate on the floor. Break it, swim down, and take the passage to the right to find a room with lots of ammo. Open the door and leave the room .Go through the passage straight ahead, where you'll find dry land.

In the next room, you'll find some Barnacles and a pool containing an Ichthyosaur. Follow the walkway around to the ladder. Climb up and talk to the Scientist, who will tell you about the tranquilizer Crossbow in the next room. There are health and power dispensers on the wall if you need them. Walk out onto the beam and drop into the shark cage to get the Crossbow. The cage will fall into the pool. Shoot the Ichthyosaur with the Crossbow until it stops moving. Swim up to get some air. Go underwater again and find the valve near the pipes. Turn it to open the grate. Swim under the grate, get the tranquilizer ammo, and walk up the stairs.

Follow the stairs up and go left at the top. In the next room, you'll see some Barnacles and some shells on a crate. When you jump on the crate, some slaves will teleport in. Kill them and enter the hallway.

	It's a difficult jump across the gap, but you need to get through that hole in the grate.

Around the corner, you'll see a wet walkway with some Ichthyosaurs swimming in a pool below. Carefully walk along it, jumping over the first gap and staying in the middle. After the first turn, the walkway will partially collapse and a slave will teleport in. If you're in the middle, you'll be OK. If you fall in, hurry to the ladder behind you and climb back up. Walk to the second gap in the walkway and jump over. It's a difficult leap to make. Once at the end, jump into the hole in the fence and swim into the passage under the sign that says "generator control."