Get yourself a short tower (with or without Ospreys nesting on the top):
Now, get yourself a tall tower:
Top them off with bright lights, then position them carefully, so the tall one shines over the short one (see below, except we're a bit too close for it to look right). You now have yourself a range light! Congratulations!! You can now safely navigate in the center of a channel by lining up the lights. If you get off course, just steer whichever direction will line up the lights again.
Happy sailing! May the waves be small and open water wide.