Take down the zombie and grab the supplies up ahead. Use the nearby barrel to jump into the pipe and swim under the water into an opening. You can smash through them with the boat, then exit the boat and look at the lambda symbol on the wall next to the pipes.

In the next area, you will rush down the canal and meet up with some Combine officers. This will raise the bridge enough for you to jump the gap with the airboat. The object of this area is to swim under the bridge with the blue containers and let them loose in the cage underneath. Then, enter the pipe next to the lambda symbol and follow it to the blue containers. A citizen will drop some supplies off the bridge ahead, so exit the boat and obtain it. Jump into the next area and take a right. Retrieve the supplies and get back into the boat.Continue up the river until you reach a ramp. Then, go up another ladder and remove the barrel blocking the gear and supplies and ammo will drop into the river below. Knock the crate out of the way, and look out for a headcrab that drops from the roof. Climb the ladder at the back of the building and make your way across the planks on ceiling. Look out for the barrels they toss at you. Enter the building and face two approaching zombies. The G-Man is standing on top of the docks as you approach. Smash through the wooden planks blocking the exit and head towards the lambda symbol on the large building to your left. Look to the right for a lambda symbol and a ladder. Get back into the air boat and take off into the canal.

Water hazard half life 2