A method and system are provided for marking marine channels. A single laser beam is selectively interrupted to produce an identifying on/off laser beam sequence distinguishable by the human eye. The laser beam is then expanded in terms of beam diameter during specifically timed periods of laser beam transmission. The expanded laser beam is projected along a beam path that is substantially along the center of a marine channel to be marked at a height above the water's surface. The height of the beam path is selected such that marine traffic may pass under the beam path without obstructing same.