Question 321Navigation General

The correct answer is C) A spherical topmark. A lighted safe water mark is fitted with a spherical topmark to aid in its identification. This is in accordance with the International Association of Lighthouse Authorities (IALA) Maritime Buoyage System, which is the standard used for marking navigable waterways. The spherical shape of the topmark helps distinguish the safe water mark from other types of buoys and beacons. The other answer choices are incorrect because: A) a red and white octagon is the shape of a regulatory buoy, not a safe water mark; B) red and white retro-reflective material is a general feature of many buoys, not specific to safe water marks; and D) a sequential number is not a physical feature of the buoy itself, but rather a means of identification.