Most recreational sailing collisions at sea don't happen because someone didn't know who had right of way. They happen because someone assumed the other vessel saw them. AIS, radar, and VHF reduce this risk but don't eliminate it. The only reliable solution is a proper lookout, a systematic bearing check on every vessel in your vicinity, and early decisive action when the bearing doesn't change.
Rule 5: The Most Violated Rule in the ColRegs
Rule 5 states: "Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision."
In practice, this means a human being who is watching — looking at the water, not the chart plotter. GPS watching is not a proper lookout. An AIS display that shows vessel tracks is not a proper lookout. A watch-keeper who is below making coffee every fifteen minutes is not maintaining a proper lookout. The rule requires continuous awareness, using all available means, which includes electronics but is not satisfied by electronics alone.
This matters because AIS does not cover all vessels. Many fishing vessels, small powerboats, and older commercial vessels either do not carry AIS or carry Class B transponders that are frequently not visible on a small-boat display. Vessels at anchor in a crowded roadstead may not be transmitting. A proper lookout means eyes on the water as the primary input, with electronics as supplementary information.
The standard of a "proper lookout" has been tested in maritime courts repeatedly. A vessel that relies solely on radar in restricted visibility and fails to post a listening watch has been found to be in violation of Rule 5. The rule is comprehensive. It is also the rule most systematically ignored by shorthanded crews on passage, particularly at night when the temptation to rely on electronics and get some sleep is greatest.
The 2-Minute Bearing Rule
The fundamental test for whether you are on a collision course with another vessel is simple: take a bearing to the vessel, wait two minutes, take another bearing. If the bearing has not changed and the vessel is closer, you are on a collision course. Act immediately.
This is called the constant bearing, decreasing range (CBDR) situation. It is the universal collision indicator and it works regardless of the other vessel's type, speed, or course. A bearing that is drawing forward (moving toward your bow) means the vessel will cross ahead of you. A bearing that is drawing aft means the vessel will pass behind you. A bearing that stays constant while the vessel gets larger in your field of view means impact.
The two-minute interval is a guideline. In a fast crossing situation in a busy shipping lane, two minutes may be too long. In a slow-developing situation offshore, you may have more time. The principle is to take the bearing, note the compass heading to the target, wait a defined interval, and check it again. Doing this systematically for every vessel in your vicinity is the core of collision avoidance in practice.
Modern chartplotters and dedicated collision alarm systems can automate this calculation if you have AIS data. A good MARPA-capable radar can track targets and compute their closest point of approach automatically. Use these tools. But understand the underlying principle so that you can apply it manually when the electronics fail, when the target doesn't have AIS, or when the picture isn't clear.
Making Your Response Obvious: Rules 8 and 16
Rule 16 requires the give-way vessel to take "early and substantial action to keep well clear." Rule 8 specifies that any action taken to avoid collision "shall be large enough to be readily apparent to the other vessel." These two rules together define what a proper evasive maneuver looks like.
A five-degree course change is not substantial, and it is not readily apparent. At a distance of several miles, in any kind of sea state, a five-degree alteration will not be visible to the other vessel's officer of the watch. It will not move the bearing significantly. It communicates nothing. A vessel that makes a series of small, hesitant alterations in a developing collision situation has not complied with Rules 8 and 16 — it has simply delayed the moment when a proper maneuver becomes necessary while the CPA decreases.
The standard response is a course alteration of at least 30 degrees, made clearly and promptly, combined where appropriate with a speed reduction. The alteration should be made before the situation is tight — Rule 16 says "early." Early means when you are still miles from the CPA, not when the other vessel is a mile away and closing.
When you alter course to avoid a vessel, you should in most cases alter to pass well astern of it. Altering to cross ahead is dangerous because it reduces the CPA and cuts across the other vessel's projected path. Bearing away to pass astern opens the distance and puts you in a position where, if you have misjudged the situation, you have room to maneuver further.
The Large Ship Reality
Sailing yachts share sea lanes with vessels that weigh 200,000 tonnes and take miles to stop. The relationship between a recreational yacht and a large commercial vessel requires a specific mindset that goes beyond knowing who technically has right of way.
A large ship at sea speed cannot stop in less than several miles. Its turning circle is enormous. Its bridge may be physically located a significant distance from its bow — on a supertanker, the bridge may be 300 meters from the ship's stem. The officer on watch has instruments, radar, and AIS to assist them, but a small fiberglass vessel in any kind of sea state with an inadequate radar reflector may not appear on their radar at all. A small vessel with no AIS, no radar reflector, and a hull that blends visually with wave patterns is genuinely invisible to a large ship in many conditions.
The practical implication is this: do not count on large ships to take evasive action, even when they are technically required to do so. Do not cross close ahead of a ship assuming it will alter course. In a traffic separation scheme, the ColRegs require small vessels to avoid impeding ships following the traffic lane. Outside separation schemes, know whether the large vessel approaching you might be constrained by its draft — if it is, you have no right of way at all, regardless of the fact that you are under sail.
If you are crossing a shipping lane — as you must in many offshore passages — cross perpendicular to the lane. This minimizes your time of exposure in the lane and makes your course easily predictable to any vessel tracking you on radar or AIS. Do not drift across a shipping lane on a long tack. Plan your crossing as a short, decisive transit at the closest to 90 degrees to the lane traffic as your course allows.
The Manual Radar Plot for CPA
If you have radar but no MARPA (automatic radar plotting aid), you can compute the closest point of approach manually with a simple technique. Plot the position of a target relative to your own vessel at five-minute intervals on a piece of tracing paper or a maneuvering board. Draw a line connecting successive target positions — this is the target's relative motion line. Extend that line forward. The closest point that line approaches the center of your plot is the CPA. If that point is close and the range is decreasing, take action.
This technique requires a stable reference: your radar must be set to relative motion display with the own-ship at the center. At five-minute intervals, mark the target's bearing and range, convert to a position on the plot, and connect the dots. Three plots give you a reliable motion line. Two plots give you a direction but not a confirmation. One plot tells you nothing about motion.
At 15 knots of closing speed, two vessels five miles apart have twenty minutes before reaching the plot position. Three plots at five-minute intervals take fifteen minutes and leave five minutes to act. In a faster-closing scenario — a ship at 20 knots and yourself at 7 knots on a converging course — the math compresses rapidly. Take bearings early and often.
The Role of VHF in Collision Avoidance
VHF channel 16 is the international hailing and distress channel. It is monitored by all commercial vessels under way and by the coast guard in most jurisdictions. A call on channel 16 to a ship that appears to be on a collision course with you — addressed by name if you can read it, or by "vessel at position X heading Y" — will typically reach the bridge and may result in a coordinated evasion.
There are important caveats. Not all small vessels monitor channel 16. A fishing vessel in an active area may have the radio on another working channel. A vessel whose crew is below may not hear the radio immediately. VHF communication is not a substitute for taking evasive action yourself as the give-way vessel — it is a supplement, used in situations where coordination will reduce uncertainty for both parties. Take the evasive action first. Then call on 16 to confirm if the situation warrants it.
The ColRegs do not reference VHF at all. They were written in an era when the practical communication tools were lights and horns. The sound signals in Rule 34 and 35 remain the legally required communication method. When a ship sounds one short blast, it is telling you it is altering course to starboard — regardless of whether either of you has a radio on. Know the sound signals and respond to them.