Another light display that you may see in resort areas, or waters that have
wrecks or reefs, is the night diving configuration. This has three vertical
masthead lights, that have a red-white-red sequence. You must maintain
a good distance from these vessels, and you should also be aware that
there may be divers near you.
Interpreting what you see
It's great that you're learning the basics of lights - what is required and when
they're required. But, this in only the beginning. You must also learn how to
interpret the navigation lights that you see when you are underway at night-
and for your safety-learn it well.
For instance, if you see a vessel approaching that shows a light pattern
such as the ones to the right, you immediately know that you are in a
crossing situation, and that you must yield to the other vessel - that's
why it is red.
Seeing a green light over a white light indicates a fishing vessel actively
trawling. You not only need to avoid the vessel, but you also need to
remember that it could potentially have a very large net deployed that
you will also need to avoid.
And there are numerous other lights and combinations of lights that you
must be able to instantly recognize - the lights for a sailboat that is privileged
over a motorboat, the special lights of various fishing vessels, a dredge or
a vessel not under command. Study the requirements for navigation from
the viewpoint of a "looker" as well as a boat owner.