(1) Zone A. Beginning at a point 250 feet west of the center line of the runway at the south end of the air strip on Northerly Island; thence 183°, 500 feet; thence 90°, 600 feet; and thence northerly to a point 250 feet east of the center line of the runway at the south end of said air strip. During the navigation season, the southeast and southwest corners of Zone A will be marked with spar buoys colored and lettered as prescribed by the U.S. Coast Guard.

(2) Zone B. Beginning at the southwest corner of Zone A; thence 183°, 500 feet; thence 90°, 700 feet; thence northerly to the southeast corner of Zone A; and thence 270° to the point of beginning. During the navigation season, the southeast and southwest corners of Zone B will be marked with spar buoys colored and lettered as prescribed by the U.S. Coast Guard.

(1) During daylight hours (from one-half hour before sunrise to one-half hour after sunset), and when the airport on Northerly Island is in operation, no vessel or other watercraft any part of which extends more than 15 feet above the water surface shall enter or remain in Zone A, and no vessel or other watercraft any part of which extends 30 feet or more above the water surface shall enter or remain in Zone B.

(2) When the airport is in operation a red ball, at least three feet in diameter, shall be continuously displayed at the northeast and northwest corners of Zone A. These balls shall not be displayed when the airport is not in operation.