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A Safe Water Mark, as defined by the International Association of Lighthouse Authorities, is a sea mark used in maritime pilotage to indicate the end of a channel. It usually implies that open, deep and safe water lies ahead, though it is sometimes also used to indicate the start and end of a buoyed section of a continuous narrow channel, or a line of these marks can be used to mark a safe route through shallow areas. It is therefore important to consult an appropriate chart to determine the exact meaning in each case. The marker is also sometimes known as a Fairway Buoy.
It is recognisable by its red and white vertical stripes and commonly bears a top-sign in shape of a red ball. Lighted buoys flash morse code "A", occulting (more light than dark), Isophase (equal light and dark) or long flash every 10 seconds (L Fl 10s).
In the United States, safe water marks have the initials of their associated waterways or localities printed on them.
Lighted buoy flashes morse code "T" (one long flash) with intervals of 6 seconds