The waters of the United States are marked for safe navigation by the lateral system of buoyage. The system employs a simple arrangement of colors, shapes, numbers, and light characteristics to show the side on which a buoy should be passed when proceeding in a given direction. The characteristics are determined by the position of the buoy with respect to the navigable channels as the channels are entered from seaward. The expression “red right returning” has long been used by the seafarer as a reminder that red buoys are kept to the starboard (right) side when proceeding from the open sea into port (upstream). Likewise green buoys are kept to the port (left) side. Red buoys are always even numbered and green are odd numbered. Red and white vertically striped buoys mark the center of a channel.