thumb|right|Examples of safe water marks
thumb|right|An example of a safe water mark in Limfjord, Denmark
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. They usually imply that open, deep and safe water lies ahead. They are also used to indicate the start and end of a buoyed section of a continuous narrow channel; and a series of them may mark a safe route through shallow areas.
- Spherical, pillar or spar in shape. For safe water marks with a spar shape, a topmark is always attached.
- Colour pattern of alternating red and white vertical stripes.
- If a topmark is attached, it is a single red sphere.
- If a light is fitted, it is white in colour and has one of the following light characteristics:
- Iso W: Isophase (repeated flashing of light with equal durations of light and darkness).
- Oc W, Oc(x) W or Oc(x+y) W: Occulting (flashing of light where the duration of light obviously exceeds the duration of darkness).
- LFl W 10s: Long flash of light (duration 2 seconds or greater) repeated every 10 seconds.
- Mo(A) W: Morse code "A" (di-dah) flashing sequence.
In the United States, safe water marks are printed with the initials of their associated waterways or localities.
See also
- Navigation
- Lateral mark
- Cardinal mark
- Isolated danger mark
- Special mark
- Light characteristic