Half-Life 2 Walkthrough - Chapter 3: Route Kanal - Barnacles and Helicopters
This section of the Half-Life 2 walkthrough covers the two barnacle puzzles and the encounter with the helicopter in the canal. These require a bit of a gameplay shift as running and jumping are required to get away with your life. The best routes are inside this guide.
First Barnacle Puzzle
As you enter the tunnel, you'll see two barnacles up ahead. You'll also notice that the floor has very little traction. Be careful and make deliberate moves and watch out for the barnacles. If you slip and one of them gets a hold of you, then look up and start shooting it as quickly as you can. It's easier to just save the ammo and use the barrels though.
Throw one of the first barrels into the two barnacles at the bottom of the first slope. Slip under them while they're trying to eat it. There's a whole pack of barnacles at the bottom of the next slope. Grab an explosive barrel and throw it down the slope. Once one of the tongues grabs it, shoot the barrel twice to set it on fire. The explosion should kill all of them. If it doesn't then they'll be busy trying to eat the bones the other barnacles cough up. Go under the barnacles and move up the exit on the right slope past the skeletons.
Second Canal Battle
They're already tossing explosive barrels into the water, so be ready for a fight. Just jump in and stay below the surface to avoid the blasts. Swim down the canal until you hit the gate and look for the ladder up to the platform on the right. Get past the gate and jump back into the water. Swim to the end and then turn around to get onto the slanted platform on the left side that has fallen into the water. This is your ramp. There is a raised board near the base next to a dead civilian. Stop here and use it for cover while you pick off the combine lining the canal. Then run along the platform and jump to the other side and double back to duck into the next sewer entrance.
Time for a quick seesaw. Just pick up cider blocks and lay them down on the high end of the seesaw to create a ramp up to the second level. It should take about six. Be careful about knocking them off when you step up to the ramp.
Time to run. I strongly suggest you save. There's a Combine hunter helicopter up ahead and it will chase you with machine guns blazing. There is nothing you can do to kill it without cheating. You have to run and hide.
Turn left and run forward. Duck under that little wood structure before the water. The helicopter should send a barrage into the wood. You'll be hit, but you shouldn't take much damage. As soon as the gunfire stops, run out and turn to the left. Take cover behind the concrete slab until the gunfire stops. Try to take out the barnacle by the stairs if you can.
Then charge up the stairs and around to the blue door. Crouch behind the barrels for cover and then open up the door. Push the barrel away and move inside. Go along the path and go down the ladder to pick up some health underneath. Climb back up and turn to the left. Crouch under an alcove and get more health. Also take the time to drag out the barrel for the next puzzle.
Second Barnacle Puzzle
This is the exact same barnacle puzzle, but it's a bit harder. Throw one barrel down and kill the first row just like you killed the ones in the beginning. If you are lucky, then the shrapnel will distract the second row and you can run past. Otherwise, grab the other explosive barrel from under the alcove and use it to clear the way. Duck into the room.
There's another batch of barnacles here. Throw one barrel down and kill as many as you can. Go quickly and slip under the rest while they are distracted. Stick to the left and jump off the path to avoid the second row. Walk outside.