At sea, I think it is safe to maintain the assumption that you are not seen by other craft, and then take appropriate measures to give yourself a wide berth from traffic wherever possible. That said, from time to time we may find ourselves a bit too close for comfort and want some assurance that we are in fact being seen by other craft out on the water.
In addition to the prescribed use of lights at night and when there is poor visibility, we take a few additional precautions. First and foremost, there is absolutely no substitute for a good set of eyes and ears keeping a constant watch and listen on the horizon. A small course correction at the first indication of CBDR (constant bearing, decreasing range), also known as being on collision course with another vessel, will help avoid close quarters avoidance tactics like crash gybes/tacks. Second, we have a large blipper type radar reflector positioned about half way up the mast on the leading edge. Other vessels we’ve spoken to on the radio indicate that this helps us show up quite well as a radar target.
With a white hull and sails, we’re generally easy to spot on a clear day, but at night, we can be pretty much invisible, particularly when there may be other traffic showing lights, or when we’re close to a shoreline where there are lights on the horizon. Where there is any doubt that we are being seen by oncoming traffic, we will contact the vessel on the VHF radio to establish that they have us in sight. We’ve found that we get a response about 90% of the time from commercial and fishing traffic, somewhat less from other cruising yachts.
If the vessel we’ve contacted does not have a visual on us, or if there is any doubt which vessel they have spotted, we have a couple of additional options. Our masthead light unit contains a strobe light for which we have a switch in the cockpit. A five or ten second burst from the strobe light invariably helps the other vessel to establish visual contact. In extreme cases, we also have the option to turn on spreader lights to illuminate deck and sails.
AIS is an interesting concept and definitely on our “radar screen.” I’m still trying to justify cost with the actual number of times in a year that we actually find it necessary to make contact with a commercial ship. In 2007 we logged about 7,300 nautical miles and actually found it necessary to contact shipping traffic perhaps four or five times. Does it really make a difference to have the ship’s name, course, etc? I don’t know.