Left 4 Dead/Boathouse Finale

Paths
After exiting the safehouse, you should reach one final street. The street is wide open and will have infected simply waiting about. It is also prone to trigger a horde.

Go through the lit building to proceed. There is usually ammunition within the building, and it provides a good defense against any triggered hordes in the region. Proceed through the back door to a wide-open campground.

The campground has a small shack which may contain a first-aid kit, but will also have pills. It's exit is a visible set of stairs around a forested region.

After the stairs should be the dock with many surrounding buildings. Head to the main boathouse.

Finale

 * The rescue boat claims to take about "10 minutes" to arrive.
 * A tank arrives when the boat has an eta of 3 minutes, and a second one appears a while after the boat reports an ETA of 2 minutes.
 * When the boat arrives after the second tank is defeated, he uses a loud fog horn to attract your attention, as well as the attention of an additional wave containing a tank.
 * The mounted gun has poor coverage - it doesn't swivel all the way to the left to cover a major angle of attack.

Exploits

 * At the corner of the map near the boat dock, there is a rock. Jump onto the rock (using crough jump) just slightly off the nearby wall, even though this doesn't appear to be the lowest point.  Move to the back of the rock when you hear a tank approaching; this causes the tank to simply disappear.  The only weakness of the boulder are smokers and hunters approaching from the water.  (Valid for November 9, 2009 version.)