Half-Life 2 Walkthrough - Chapter 4: Water Hazard - The Second Flood Gate
This section of the Half-Life 2 walkthrough covers the entirety of the battle at the second flood gate. You will need to kill a bunch of Combine while dodging the gunfire of a pursuing helicopter. This is actually one of the toughest parts of the game so far, so feel free to look inside.
The Second Flood Gate
You're safe for the moment. The path straight ahead is blocked so stick to the right. Stop at the little pulley system and notice the supplies out of reach. Pull the two concrete blocks out of the one basket to make the other fall. Grab the health and energy as well as some ammo for the Magnum which you'll get in a second. Get back in the boat and drive out to the end.
You will see the flood gate ahead close with a soldier on the outside shooting at you. Drive past him quickly and just ignore him for now. Pull up to the docks and shoot the lock off of the door. Go inside and then grab all the goodies off the table. Make sure you get the .357 Magnum. It can kill any soldier with one hit. It's also one of the most accurate guns in the game. Three men are on the other side of the door. The submachine gun is probably better suited to killing these three. Then pull out the Magnum and charge up the steps. Kill the one soldier at the top. Then save! This can go wrong really quickly if you get lost.
The helicopter is back and its strafing you. Run out between the two shipping containers and shoot the soldier hiding in the blue container to the right. If you aren't fast enough, he can release a man hack that you'll need to shoot too. You can take cover in this container when the gunship swings around. Once it stops shooting, rush out and run straight ahead. You should be able to make it all the way around the u-turn and into the open container if you sprint by holding down “Shift." Duck behind the closed door to stay safe from the barrage. Break open the boxes and run out again. Look to the left and dash into the warehouse. There's about 2 soldiers on the ground and two on each of the catwalks to the right and left.
Start clearing out the soldiers in whatever manner you choose. The magnum is handy for the one's at a distance on the catwalks. Go to the back right corner and climb up to the catwalk on the right. Go to the end and jump onto the containers to cross to the other side. Another 2 soldiers will come out onto the ground floor and two more will charge in from the other catwalk. Kill them with whatever you have.
Opening the Flood Gate
Go through the door and stick to the left side. Crouch under the windows to avoid the helicopter's gunfire. Break the boxes at the end and go through the door. There's a soldier to the right. Surprise him and take him out with the submachine gun or the pistol. Two more come up the stairs, so take them out too. Go down the stairs and take cover right by the health charger and the suit charger. You should be safe from the helicopter if you stay behind the little bit of wall.
Charge up your health and armor, then rush out and get behind the container ahead. Turn to the right and look for the opening in the fence to get along the sloped pathway. Kill the soldier in your way and run down to the ladder by the guard tower. The soldier who was shooting at you when you first docked will charge toward you. Kill him and then climb the ladder. Don't go all the way up though. Go high enough to see into the tower and see the two guards inside. Kill both soldiers. Then man the machine guns and open up on the helicopter. Shoot at it until all three engines catch on fire and it flies away. Press the button to open the gate. Time for you to leave. Go down the ladder but don't backtrack. Just go out onto the ledge by the water. Go to the end and you should see your boat at the docks. Jump into the water and swim out to it. Jump inside and go out to the gate.