Lateral mark (IALA)

A lateral mark is an IALA buoy or beacon that marks the side of a well-defined channel, read in the conventional direction of buoyage from seaward toward harbor. In Region A the port-hand mark is red with a can shape or red can topmark and the starboard-hand mark green with a conical shape or green cone topmark; Region B reverses the colors, red to starboard. When lit, lateral marks show a rhythm of their own color, commonly a flashing or group-flashing light. The mariner keeps the port-hand marks on the port side and starboard-hand marks to starboard when proceeding in the buoyage direction. Lateral marks are the only IALA mark type whose color depends on the region.