The correct answer is A) high water line. The shoreline on nautical charts generally represents the mean high water line, which is the average high tide line. This is the standard used for charting shorelines, as it provides a consistent reference point for navigation and mapping purposes. The other options are incorrect because: B) low water spring line refers to the lowest tide levels during spring tides, which is not the typical shoreline depicted on charts. C) low water line is even lower than the low water spring line, and would not accurately represent the typical shoreline. D) tide level is a general term that does not specify which tide level is being referenced.