Question 294Navigation General

The correct answer is D) Mean high water. The height of a navigational light is measured from the mean high water level, which is the average of all high tide levels over a 19-year period. This is the standard reference plane used for measuring the height of lights and other aids to navigation, as specified in Coast Guard regulations. The other options are incorrect because they do not represent the appropriate reference plane for measuring light heights. Geographical sea level, mean low water, and average water level are not the standard references used for this purpose.