The correct answer is C) numbered. Port side daymarks are required to be numbered to indicate their position along a channel or waterway. This is a regulatory requirement established by the United States Coast Guard to help mariners navigate safely. The numbering of port side daymarks is a standard practice that allows boaters to identify their location and progress along a marked channel. The other answer choices are incorrect because: A) port side daymarks are not of any shape, they must be a specific shape, typically can-shaped; B) port side daymarks are not octagonal, that shape is typically reserved for regulatory signs; and D) port side daymarks are not required to be black and white, they can be painted in various color schemes to enhance visibility.