Cardinal Buoys are used to indicate the position of the hazard and direction of the safe water to which the vessel should pass. Cardinal buoys by their top marks indicate the direction of safety as a cardinal (compass) direction (north, east, south or west) relative to the mark. The presence of top mark helps the navigator in easily identifying the type of Cardinal Buoy and the direction of the safe water where the vessel must proceed. The "Top-marks" being clearly visible reduces the chances of error.