Sailing Safety Guides

Collision Avoidance

Collision Avoidance And Lookout Under Sail

Collision avoidance starts before the alarm. It starts with a real lookout.

Electronics help, but a skipper still has to look, listen, think early, and make a clear decision before the distance becomes small.

First Principle

A screen is not a lookout

AIS, radar and plotters are useful. I like them. But they are not the sea. A proper lookout also uses eyes, ears, compass bearings, sound, lights, wave shape, common sense and enough time to think.

The dangerous mistake is quiet confidence: the autopilot is steering, the plotter looks calm, the AIS list looks acceptable, and the skipper stops checking the real world.

What a lookout is really doing

A lookout is not only searching for ships. A lookout is building a picture of what can hit the boat, what the boat can hit, and what might change before the next check.

Vessels: ships, fishing boats, ferries, workboats, small craft and sailing boats.
Unlit or poorly lit objects: buoys, fish traps, nets, floating debris and moorings.
Land and depth: headlands, rocks, reefs, sandbanks, lee shore and traffic lanes.
Weather: rain squalls, fog, lightning, glare, darkness and sea clutter.
Your own boat: sail plan, speed, steering mode, visibility from the cockpit and fatigue.

Constant bearing, closing range

A simple practical warning is this: if another vessel stays on the same bearing and gets closer, collision risk may exist. The bearing can be checked by compass, hand-bearing compass, a stanchion, a mark on the sprayhood, or a repeated visual line.

If the bearing does not move, do not wait for perfect certainty.
If the other vessel is large, fast or close, give yourself more margin.
If you are unsure, assume risk exists until you understand the situation.
Check again after any course or speed change.

AIS is not everything

AIS is excellent for many targets, but it can also create false calm. Not every vessel transmits AIS. Some small craft, fishing gear, tenders, floating objects and poorly maintained systems will not appear as a clean target.

Use CPA and TCPA alarms, but tune them so they are useful.
Watch for targets without good heading, speed or identity data.
Remember that a target can turn, stop, fish, tow gear or make a course change.
Do not ignore what your eyes say because the AIS looks acceptable.

Radar helps if it is understood

Radar can see rain, land, many vessels and some objects that AIS cannot. It also has limits: sea clutter, rain clutter, range scale, antenna height, target size, tuning and operator skill.

Practice in easy conditions before trusting it in rain or darkness.
Use longer-range scans for early warning when power allows.
Use guard zones carefully; too many false alarms can train the skipper to ignore them.
Small boats, low objects and floating debris may still be missed.
Plot or systematically observe targets, not only one quick glance.

How to read AIS danger

AIS is most useful when it is treated as a moving problem, not a list of names. The first question is not "what is the ship?" but "will our distance still be safe in ten, fifteen or thirty minutes?"

CPA is the predicted closest point of approach. Small CPA means little passing distance if both vessels keep moving as now.
TCPA is the time until that closest point. A small TCPA means there is little time left to make a calm decision.
Watch the bearing trend. A target with steady bearing and decreasing range deserves attention even if CPA looks acceptable.
Check data quality. Missing heading, stale position, strange speed or no vessel name means less trust.
Fishing boats, tugs and workboats may turn or tow gear. Give them more room than the AIS triangle alone suggests.

How to use radar without fooling yourself

Radar is powerful, but the wrong mode or wrong gain can hide the target you need. Coastal, harbor, offshore, rain and bird modes are only starting points. The skipper still has to look at the screen and ask whether small targets, rain and sea clutter make sense.

Use range scales deliberately: longer range for early warning, shorter range for close detail.
Too much gain fills the screen with noise; too little gain can erase weak targets.
Sea clutter can hide small craft in waves. Rain clutter can hide traffic inside a squall.
Try guard zones in easy conditions before relying on them at night.
If radar and eyes disagree, slow down and investigate instead of trusting the nicer answer.

VHF can help, but it must be usable

A short VHF call can clarify intention when there is still room, but it does not replace early collision-avoidance action. Keep the volume high enough to hear calls, keep squelch low enough to hear weak stations, and do not wait for a radio conversation before taking a safe maneuver.

Night and bad visibility

At night, the boat can feel private even when it is not. Lights can be confusing. Rain can hide targets. A tired skipper can stare at a screen and miss what is outside.

Look outside before trusting the instruments.
Check navigation lights are working and not blocked by sails or gear.
Use the VHF volume sensibly in open water.
Shorten rest intervals near traffic, land, fishing areas or poor visibility.
If visibility falls, slow down and give yourself more time.

Fishing vessels and small craft

Fishing vessels may not behave like simple traffic targets. They may tow gear, turn unexpectedly, work slowly, show confusing deck lights, or have gear extending far outside the hull.

Give fishing vessels more room than the hull alone suggests.
Look for floats, flags, pot markers and gear lines.
Expect small craft without AIS, especially near shore.
Use clear early course changes instead of passing close and hoping.

Early action should be obvious

A small nervous course change late is often worse than a clear early one. If there is room, make your intention obvious and check that it is working. Avoid a series of tiny changes that confuse the other vessel and do not create real separation.

Act early enough that both boats have time.
Make a course or speed change large enough to be understood if the situation allows it.
Check the bearing again after the action.
Do not create a new danger with land, shallow water, other traffic or waves.
If needed, use VHF, sound signals or engine to clarify and create margin.

Stand-on does not mean asleep

If your vessel is expected to hold course and speed, that predictability helps the other vessel make a clear avoiding action. But standing on is not the same as switching off. Keep watching. If the other vessel does not act, or if the situation is becoming unsafe, use sound, VHF, engine or a clear maneuver while there is still room.

The aim is not to be clever with the rules. The aim is that both skippers can understand what is happening early enough to avoid a close-quarters surprise.

Autopilot blindness

An autopilot can hold the course beautifully while the skipper slowly becomes a passenger. The danger is not the autopilot. The danger is believing that because the boat is steering, the watch is being kept.

Set a watch timer even when everything looks calm.
Make each check real: outside, instruments, traffic, weather and boat sound.
If you are too tired to keep a lookout, reduce risk before sleeping.
Do not let a quiet cockpit become permission to stop navigating.

A simple traffic check rhythm

Step	Check
1. Outside	Horizon, lights, silhouettes, wave shadows, sound and anything visually wrong.
2. AIS	Closest targets, CPA/TCPA, target behavior and missing information.
3. Radar	Targets without AIS, rain, land, clutter and guard zone state if fitted.
4. Own boat	Course, speed, sail plan, steering mode and whether you can maneuver now.
5. Next margin	Will this still be safe at the next check, or must action be taken now?

How this connects to SailingKSF

This article connects directly to night watch discipline and the AIS tools in the SailingKSF suite. Instruments can warn, but the skipper still has to understand the situation and act early.

Night Watch Sleep Safety AIS Dispatcher Calling For Help At Sea

Related DSC and AIS check

If this article makes you rely on DSC, MMSI, AIS, CPA/TCPA or AIS MOB, open the separate DSC and AIS check in a new page and verify the setup before passage.

Open DSC And AIS Check

USCG Navigation Rules - Official USCG navigation-rules text, useful for lookout, safe speed, collision risk, lights, shapes, anchoring, towing and distress signals.
USCG NAVCEN AIS FAQ - Official AIS background and limitations. AIS is very useful, but the data must still be checked against lookout and radar.
RYA radar course overview - RYA overview of why radar is valuable but can mislead if controls, setup and limitations are not understood.
Garmin radar tuning and operation - Practical explanation of gain, sea clutter, rain filtering and radar range modes from a marine-electronics maker.
IMO COLREG Convention overview - International background for the collision regulations. Use it as the official convention context, then check the rules that apply where you sail.
UK Marine Accident Investigation Branch - Official accident reports and safety digests. Useful for seeing how small decisions, gear failures and fatigue can grow into serious incidents.

App Connection

Use this together with KSF Passage Companion

The articles are easier to use on a real boat when your own boat details are already written down.

Store where safety gear, tools, spares and manuals are located.
Keep boat-specific checklists for night, heavy weather, departure and emergencies.
Use logbook notes for failures, chafe, repairs and weak points that should be checked again.

Open Passage Companion Open Printable Cards

Feedback For Collision Avoidance And Lookout

If you have practical experience with lookout, traffic, AIS, radar, fishing vessels or close-quarters situations, I would be glad to read what should be added.

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Look early, decide early

A good collision-avoidance action is usually early, clear and boring. Last-second cleverness is not a good navigation plan.