Half-Life 2 Walkthrough - Chapter 4: Water Hazard - Avoiding the Mines
This section of the Half-Life 2 walkthrough will give you the best methods for avoiding the mines and escaping the new helicopter on your tail. The little seesaw puzzle ahead gets a mention too, so if you are stuck at any point between the second and third flood gates, then look here.
Third Canal Run (The One with the Mines)
It's time to keep driving. A helicopter flies in and will start to drop mines into the water. There isn't a scripted path, so I can't give you much advice. Just try to avoid them and don't fly right behind the helicopter. You can also hit a few of them without taking much damage overall. One mistake won't kill you.
Swing to the right to avoid the ships blocking your path and just follow the route for now. You'll need to pull off a powerslide to get across a u-turn, but it shouldn't be too hard. Just act like you're turning right at the top of the ramp, but hold onto it too long to finish the slide. Then just keep flying along while dodging the mines until you get into another tunnel and hit a loading screen.
The helicopter is waiting for you at the end. Head straight toward it and keep going. The path is fairly linear. Just keep dodging mines and ships until you come to a little dam. Then just get up onto the land next to it to hope right over. Just keep going and turn into the series of sewer pipes. Save now! You will thank me.
Running Along the Pipes
Pray that the helicopter doesn't drop a mine through an opening in this pipe tunnel. Move through until you curve around to an outdoor area. This is what I had you save for. The best way to do this is to skip across the sections of pipe by going at full speed until the end. Don't try to maneuver much. Any movement will probably make you fall. Just try to line up with the pipes and ride it to the end. If you fall off, you'll probably be killed by the helicopter while you try to get back up to the pipes.
Keep going until you hit the loading screen. Take the path to the right and go up the makeshift ramp to get past the blockade. Then run down the canal for a bit past a few bridges. Watch for the warehouse on the right. It's big and red and has a large ramp leading up to it. Save and try to take the ramp just right. You want to ideally land on the ledge by the warehouse. Then drive inside and park on the little trolley system. There is a health charger and a suit charger in the corner. Stay alert though, since the helicopter is still hovering over the warehouse. When you're ready, you can lower the airboat down to the waters below and leave. If you do miss the jump, then you have to go to the waters under the warehouse and climb a ladder to get the health.
Go forward and get out into the water as the mortars start to fall. The smokestack in front of you will take a direct hit and crash. Slow down and then fly right over a curved section. Drive fast and zig zag to avoid the rockets from an armored car and get into the sewer pipe it's guarding.
There's another seesaw puzzle ahead. Park the airboat by the middle of this T-section. Get out and look at the ramp. You need to have a lot of weight in the little elevator to make the ramp rise up. Pull the lever now and break open the supply crate inside. Then go back into the sewer part and look for the ladder on the side. There's a zombie that will burst out of the water if you go for the supply crate in the water.
Climb the ladder and then get onto the walkway until you drop down onto the top of a pipe. Walk across the ladder to get to the other side and drop down to the second floor of that ledge. Push the big washing machine down onto the released elevator. This will be enough to raise the ramp. Drop down and get into the airboat to jump out.