Spoil ground marks Military exercise zone marks Cable or pipeline marks, including outfall pipes Recreation zone marks Another function of a special mark is to define a channel within a channel (for example, a channel for deep-draft vessels in a wide approach area where the limits of the channel for normal navigation are marked by red and green lateral buoys). Yellow is the color used for special marks. The shape of a special mark is optional but must not conflict with a lateral or a safe-water mark. When a topmark is carried, it takes the form of a single yellow X. When a light is exhibited, it is yellow. The phase light characteristics may be any other than those used for white lights of cardinal, isolated danger, and safe-water marks. NEW DANGER A newly discovered hazard to navigation, not yet shown on charts or included in Sailing Directions or sufficiently announced by Notices to Mariners, is called a “new danger.” New danger covers naturally occurring obstructions, such as sandbanks and rocks, or man-made dangers, such as wrecks. A new danger is marked by one or more cardinal or lateral marks, following the IALA Maritime Buoyage System guidelines. If the danger is especially grave, it will be marked by two marks that are identical until the danger has been announced. If a lighted mark is used for a new danger, it must be a quick flashing or very quick flashing light. If it is a cardinal mark, it must exhibit a white light; if a lateral mark is used, it must exhibit a red or green light. AIDS IN THE INTRA COASTAL WATERWAY 9-19 The Intracoastal Waterway, called the inland waterway, is a channel in which a lightdraft vessel can navigate coastwise from the Chesapeake Bay almost to the Mexican border, remaining inside natural or artificial breakwaters for almost the entire length of the trip. The following paragraphs describe special markings for the Intracoastal Waterway proper and for those portions of connecting or intersecting waterways that must be crossed or followed in navigating it. Every buoy, daymark, or light structure along the Intracoastal Waterway has part of its surface painted yellow, the distinctive coloring adopted for this waterway. Lighted buoys have a band or border of yellow somewhere. Red buoys and daymarks are to the right, and green to the left, as you proceed from the Chesapeake Bay toward Mexico. As in other channels, red buoys have even numbers; green buoys, odd numbers. Because the numbers would increase excessively in such a long line of buoys, they are numbered in groups that usually contain no more than 200 buoys. At certain natural dividing points, numbering begins again at 1. Lights on buoys in the Intracoastal Waterway follow the standard system of red or white lights on red buoys, and green lights on green buoys. Lights on lighted aids besides buoys also agree with the standard rules for lights on aids to navigation. RANGES Two daybeacons located some distance apart on a specific true bearing constitute a daybeacon range. Two lights similarly located comprise a lighted range. When a ship reaches a position where the two lights or beacons are seen exactly in line, it is on the range. Ranges are especially valuable for guiding ships along the approaches to or through narrow channels. Lights on ranges may show any of the four standard colors, and they may be fixed, flashing, or occulting, the principal requirement being that they stand out distinctly from their surrounding. Range light structures are usually fitted with colored daymarks for daytime use. Range lights appear to lose brilliance rapidly as a ship veers from the range line of bearing. Ranges should only be used after a careful examination of the charts; it is particularly important to determine how far the range line can be followed safely. This information is available on the chart. FOG SIGNALS Most lighthouses, light towers, and large navigational buoys are equipped with fog-signaling apparatus, generally sounded automatically by mechanical means. For purposes of identification, each station has its own assigned number of blasts, recurring at specified intervals. A definite time is required for each station to sound its entire series of blasts, providing additional identification.