Half-Life 2 Walkthrough - Chapter 4: Water Hazard - First Station to the Flood Gate
You are now racing through the water in a half-destroyed airboat and you might need some help. This part of the Half-Life 2 walkthrough will cover the first part of chapter 4 and the driving up to the first flood gate.
Zombie Barn (Optional)
If you really need more health, then swing over to the barn on the right just outside of the main gate. If you don't, then just skip it. There are friendly resistance soldiers ready to help you...well, they were ready. They're zombies now. Kill the two zombies on the first floor of the barn and then go up the broken steps to the boards up top. Pull out the crowbar and stick to the sturdy boards on the left as you move toward the ladder. A headcrab drops down the ladder when you reach it, so smack it with the crowbar. Climb the ladder and look at the supplies hanging out the window. Knock the barrel out of the winch with your crowbar and then take a leap of faith into the water below. As long as you don't hit anything in the water, you won't be hurt.
Get into the boat again and go over the ramp. Another resistance soldier will throw some crates into the water for a quick ammo refill. Drive over them to pick them. Drive up to the sunken ramp and park it.
This is another seesaw puzzle. You need to use the empty blue barrels to raise the ramp up enough for the jump. You just need three more for the cage below the ramp. Go through the open sewer pipe to the left of the ramp. Walk through the tunnel as it curves to the end. Knock both barrels into the water and then jump in. Grab the last one off the ledge by the ramp and then save up your oxygen for a second. Grab a barrel and swim under the ramp. Release the barrel into the cage below. Rinse and repeat until they're all in it. Go back out to the boat and jump the ramp.
First Canal Run
Time for a little conflict. Dropships are releasing troops ahead. There isn't any great way to fight them. Run over them if you want, but don't stop. They won't be able to hit you often, if you just stay mobile. Just swing around the bend past both groups of soldiers and look for the ramp along the left side of the canal. Go up it and try to land on the wooden platform for a cool maneuver.
There are more soldiers up ahead and the one with a submachine gun is creeping his fire toward you. Swing out of its path and then smash through the wooden supports to dump the soldiers into the water. Swing to the left of the canal and drop out into some clean water and a loading screen.