Operating in restricted visibility. And the dangers!

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Firstly, what is restricted visibility?

Many people consider restricted visibility as fog or heavy rain but the hours between sunrise and sunset are all regarded as restricted visibility. Any condition or situation that restricts your ability to see clearly or hampers your vision is restricted visibility!

In fact, the hours leading up to daylight and sunset can make visibility exceedingly difficult depending on your course in relation to the rising or setting sun.

Operating in restricted visibility. And the dangers!

Most of us have had to operate in these sort of conditions at some time or another and hopefully survived without incident!

By following a simple procedure (you do have one don’t you?) you can make it safer not only for yourself but others as well.

Here’s a guide to good seamanship when operating in restricted visibility.

  1. Always proceed at a safe speed relative to the conditions
  2. Maintain a watch by sight, sound, including your radio and all other available means
  3. Where necessary use the appropriate sound signals (see Sound Signals below)
  4. If a close quarters situation exists you must take appropriate action to avoid a collision (collision means not only with another vessel but also navigational markers or beacons, etc.)
  5. At all times monitor the radio
  6. If other vessels are nearby broadcast your intended movements

Sound Signals

These sound signals are to be used when operating in restricted visibility.

  1. Underway:sound at intervals of not more than 2 minutes apart 1 prolonged blast;
  2. Underway but stopped: sound at intervals of not more than 2 minutes 2 prolonged blasts in succession with an interval of 2 seconds between them
  3. At anchor:ring the bell (if fitted) rapidly for about 5 seconds

When you’re operating in restricted visibility it’s vital that you follow this procedure to ensure the safety of your vessel, all persons onboard and other vessels!

It’s important that you comply with the regulations at all times and for this procedure you can go to the COLREGS Rule 9 – Conduct of vessels in restricted visibility.

Shorlink’s Recommendation

We strongly recommend placing a lookout on the bow when operating in close proximity to other vessels, entering port where manoeuvrability may be restricted or where other potential dangers exist.

Operating from the wheelhouse where vision is impaired by fog, heavy rain, sunset, sunrise or any other condition can make navigating more difficult.

You may have your sight impacted by interior lights, lights from gauges and/or navigational equipment or other things all of which can cause significant issues. By using a forward lookout, you minimise the risks!


Remember that during periods of heavy rain or other conditions your radar may be impacted and not display potential dangers, especially other vessels. When operating in close proximity to other vessel ensure you maintain communications by using your radio.

This is such a simple action but unfortunately many collisions occur due to a failure to communicate!