The Castle Harbor Marina Basin encompasses the area beginning at the east end of the north jetty at or near Lat. 38° 59.432' N., Long. 76° 16.685' W., then running 120° (True) to the east end of the south jetty, at or near Lat. 38° 59.415' N., Long. 76° 16.648' W. and running to the head of the Basin. This area has a 6-knot speed limit all year.