Half-Life 2 Walkthrough - Chapter 4: Water Hazard - The First Flood Gate
This part of the Half-Life 2 walkthrough covers the fighting you'll have to do to open the first flood gate. The canal run after it will also be covered for anyone who is having trouble with the airboat sections.
The First Flood Gate
Once the area loads, you should see one combine soldier firing at you from a bridge. Ram the supports to kill him now. The gate up ahead is closed and the controls are up there. Stop the boat by the stairs and jump out. Use the ladder to climb up to the guard station and go inside. There are two soldiers hiding around the corner, but don't worry about them yet. Go into the two supply rooms across from the entrance room. Pick up the ammo, health, and grenades. There's also an ammo crate with infinite grenades by the rooms, so stock up now. Toss a grenade around the corner to kill the two soldiers by the armored car in the corner. Then charge the spot where they were and shoot the glass windows shielding another combine. He's busy releasing the four man hacks, so throw a grenade through the broken windows and into his room. Pick off the survivors with submachine gunfire.
There's a health charger in the room and another ammo crate with grenades. Heal up and then go to the door. Decide on a strategy first though. There's a machine gunner ahead.
There's a machine gunner guarding the door across from you. You have two options. You can throw a grenade at him to make him step away from the gun. This is a little risky since you can miss and lose a lot of health. The safer route is to run straight out and duck behind the barrel. Pick up the barrel and hold it in front of you as a shield. He won't fire if he doesn't have a line of sight. Get as close as you can and drop it right in front of the gun. He'll abandon the position and you'll be able to land a head shot at point blank range. Remember to move the barrel though, since that gun will be your best friend in a second.
Opening the Gate
Open the door he was guarding and toss a couple grenades around in a spread. Wait for the explosions to stop and charge into the room. There are two men on the floor and one manning the catwalk on the left. Pick off the survivors and grab more grenades from the ammo box in the room. Also use the health charger to heal any damage. Go up to the other catwalk and open the door. The valve to open the gate is sabotaged, but they forgot about the full physics system. Turn to the right and shoot the explosive barrels to knock out the support lines holding up that stack of steel beams. Then watch your makeshift ram blow the gate apart.
Backtrack to the machine gun position and kill the guards rushing through the door to your position. Then move back to the room with all the armored cars. Throw grenades behind the cars in the first half to kill the first few soldiers. Another Combine is using the machine gun position at the start. Peek out from around the corner and then toss a grenade into his corner to blow him away.
Leave and drop down to your airboat. Then drive through the newly opened the gate to the next area.
Second Canal Run
You certainly will be running. Build up speed and swing along the canal to the left. Watch the armored car on the ridge in front of you. It will start shooting rockets, so I strongly suggest that you keep moving. Try to drive away from the rockets but don't lose speed. Most of them will just fly over your head if you keep moving. Swing under the gap to the right but stick to the far wall to avoid the barnacles.
Pass under another bridge and watch out for another armored car. Drive fast and zig zag to try and avoid its rockets. Keep going and start hugging the right wall. The Combine start a gasoline fire in a truck on the river. Take the ramp to dodge most of the fire. Another armored car is ahead to the right. Drive fast and burst through the posts under it to get into the tunnel and reach another loading screen.