Follow the coastline past the hut (later on, you will enter the hut to find a secret). Jump across the channel and continue down the coastline. This is where you must swim through the ice-cold water. Swim quickly across to the ledge and hop out. Repeat. Make your way up by climbing the cliffs to the ledge, then monkey swing across to the cliff in front of the ship. Jump to the ship and make your way to the trapdoor and drop in.
Follow the hallway and dispose of the thugs along the way. In the chamber, make a right and head into the room with the generator. There's a switch on the wall that opens a trapdoor in that room. Drop down and follow the hallway to the room with the orange pipe. Drop down onto the trapdoor. At the end of the hallway push the button that drops the boat into the ice-cold water below. Go back in the room with the orange pipe. Jump up to the next floor and make your way to the deck of the ship. On the deck, turn right and follow the path near the cliff. Jump and grab the ledge to get your save crystal. Backtrack and jump into the water. Climb into the boat before you freeze. Take the motor raft around the ship and up the channel. Stop at the ledge in the tunnel. Jump and grab from the slope to the ledge. Light a flare to help you find your way through the dark. Go right and pick up the medi pack.
Backtrack through the crawlspace. You'll drop into the boat in the water. Continue through the tunnel to the water gate, exit the boat, and get your guns ready. On the other side of the building, climb the box and monkey swing across the bars. Follow the path through the mountain and watch out for trouble. Go through the hallway in the complex and be ready for huskies and thugs on the other side. At the other end of the hallway, push the button on the wall of the complex next to the door; then go around to the left, near the pipe. Drop down into the water and quickly swim to the ledge. From here, make your way past the fuel valves and up the ladder. On top is the sealed generator room. Turn the other way and head left toward the outside area. Go past the caged huskies. Down the path under the bridge, you'll find some ammo, but you must fight for it.
Go back into familiar territory past the hole with the fuel valves and enter the large cave. Watch for trouble lurking in the dark. At the complex, the doorway has a slamming door, so be careful. It is deadly if it closes on you. To help pass it, you can roll through. Make your way upstairs and fight your way to the crowbar. Head back through the dark path to the raised structure, throw the switch on the wall, and use the crowbar to open the door. Drop down the hatch and read the map. Now, return to the fuel valves, and turn valves two and four. Head back to the generator room and pull the switch and power up the surrounding area. Watch for the huskies and enter the building. All three buttons are now active, so retrieve the gate key from the top of the desk.
Backtrack to where you left the boat and use the key. Press the button to raise the gate. Jump backward into the boat and follow the waterway. Stop at the ledges and pick up the items at the landing to the right. Inside, you'll get the hut key. If you decide to return to the hut, you will find a save crystal and flares. Continue down the waterway through the gate and climb to the cabin. Keep a close eye out for enemies. Go around the structure toward the door and end the level.