Recognising lights at night when you're on watch at sea isn't easy, particularly if the other vessel is changing course a lot (as many fishing vessels do) or showing working deck lights which are often a great deal brighter than any navigational lights.
Once you have the basic navigation lights sorted, you can then start interpreting the information that other sets of lights are giving you.
Possibly the next most important set of lights after navigation lights are those that denote various kinds of restrictions. (I'll deal with fishing vessels separately, in another article.)
The first two are vessels restricted in their ability to manoeuvre (a restriction which belongs to the vessel herself), and vessels constrained by their draft (a restriction imposed on deep draft vessels by the nature of the channel).
The lights for 'restricted in ability to manoeuvre' (RAM) are an all-round red over white over red and for 'constrained by her draft' three all round reds. The collision regulations say that these lights shall be shown 'where they can best be seen', which may not be on the highest mast, and may be displaced to one side or other. So you can sort out the navigation lights from the 'restriction' lights.
You'll often see ferries showing RAM lights (or shapes during the day). Sometimes a vessel is restricted in her ability to manoeuvre because she has something hanging off one side or other - perhaps a cable drum, or some pipe laying equipment.
In such cases, she may well indicate to you which side you should pass. She does this by using two red two green lights in addition to the restriction and navigation lights. Guess what! You pass her on the side showing the green lights. Don't confuse them with the navigation lights, though! Use the binoculars, and if in any doubt, keep well clear.
Another two forms of restriction are when a vessel is 'not under command' or when it has gone aground! Both have the same restriction lights - two all round red lights. I remember one dark evening crossing Biscay and watching a large vessel passing us, then suddenly seeing two all round red lights appear on the main mast.
Assuming the watch officer hadn't pulled the wrong switch and that she hadn't hit a hitherto unknown sandbank, we assumed he had lost steerage or engines and was therefore 'not under command'. Needless to say, we watched her very carefully from that point.
A vessel aground at night is lit in the same way as a vessel at anchor, but with the addition of two all round red lights. So, for example, a ship over 50 metres aground will show a white all-round anchor light in the bow, and a white all-round light at the stern lower than the bow light, and in addition the two all round reds. (A vessel under 50 metres is not required to show more than one all round white light). She won't show navigation lights because she isn't under way.
So to recap, you only have to learn three different restriction lights in addition to the normal navigation lights: Red-White-Red for Restricted in Ability to Manoeuvre; Red-Red-Red for 'Constrained by Draft', and 'Red-Red' for 'Not under Command' or 'Aground'.
And when a vessel is restricted in her ability to manoeuvre, she might also tell you which side is safe to pass by showing two all-round greens, and which is not by showing two all-round reds.
Simple, isn't it?
Richard Thomas holds a Commercially Endorsed RYA Yachtmaster and Cruising Instructor (Sail) certificate. He runs his own delivery business, www.yachtmovers.co.uk
He is available for deliveries, assisted passages, own-yacht tuition, and yacht management.
