Nobody expects to encounter shallow water, but if you plan well ahead, set alarms and empower your crew you can avoid the nasty surprise of grounding your yacht

The 2017 investigation into the grounding of a Clipper Round the World yacht in South Africa delivered some interesting lessons for us all.

The most notable points were that: the skipper was the sole person in charge of navigation and became distracted by other tasks and lost situational awareness; the chartplotter was below decks and there was no route marked on it; the displays at the helm did not show depth, nor were there shallow water alarms set; and a course that started out clearing any dangers became unsafe through gradual changes to the wind direction.

Although these are just the headline mistakes in a complex case, they’ll elicit an uncomfortable feeling of recognition among many sailors. When we don’t expect to encounter shallow water, either due to planning an offshore route or sailing in familiar waters, it can be easy to miss the warning signs. Here are lessons for safeguarding against avoidable groundings.

Plan ahead

Good passage planning will not only highlight areas of concern but also enable prompt and effective corrective actions to be taken should the depth unexpectedly decrease.

Study your entire route at all levels of zoom, identify areas of concern, study the weather forecast and consider how changes to wind direction may affect your plan. If beating or gybing along a shore line, study depth contours to assess how quickly the bottom will shelve.

Using this information, set realistic depth limits ahead of time, which allow enough time to tack or gybe out to deeper water, taking into account the boat speed and how quickly you can make the manoeuvre with the current crew.

For coastal sailing the sonar charts from Navionics, which use verified crowd sourced bathymetry, can give a greatly enhanced and more up to date view of well navigated areas.

Set alarms

Alarms are a useful tool although, to be effective, like everything else on your boat they need to be trimmed. Alarms should be adjusted to reflect conditions and set to a level that will ensure they are not constantly sounding and therefore get ignored.

An audible alarm will allow less experienced crew members to comfortably stand watch and be sure of exactly when to call the skipper; they’ll also alert a skipper whose attention has been drawn elsewhere.

Shallow water

Your definition of shallow water will change depending on the type of passage you are making. If you are not expecting to encounter shallow water, study the chart and assess how steeply the bottom shelves.

Set the alarm to a level that will give enough warning to make corrective actions. Even if depth is not constantly displayed on your on-deck instruments, alarms can still be set in the background.

XTE alarm

Cross-track error alarms will sound once your track has strayed too far from the rhumb line. Ensure there are sufficient waypoints in your route to make these effective.

Wind shift

Particularly if using the auto-pilot in ‘wind’ mode, changes in wind direction can lead to gentle and sometimes (especially at night) imperceptible changes to the course sailed, which may drive a boat into danger.

If your pilot features a wind shift alarm, this is worth using. If not the XTE alarm should perform a similar function.

Radar Guard Zone

In reduced visibility the radar guard zone will help maintain a specific distance from coastlines. Once again, this distance should be set to allow enough time to make corrective manoeuvres.

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Empower your crew

Whether the skipper/navigator are on deck or off watch, your entire crew should always have a good understanding of current navigational parameters. Making sure they all know you do not expect to see depths below 20m will remove any ambiguity about what is ‘shallow’, stop unnecessary worry and empower them to speak up about something you may not have seen.

It can be difficult to remember numbers so if not using alarms, use a white board in the cockpit to record crucial information – this could be a laminated sheet of A4 paper stuck to the coach roof. Write down minimum depth, course no greater than/no less than, distance from shore etc. Review the information at the change of each watch.

Set up chart plotters to be as visual as possible. Depth contours can be shaded and no-go zones can be drawn onto charts and shaded. Marking charts up in this way removes any need for chart interpretation by inexperienced crew and can be backed up with an order to: “Wake me if we enter the red zone”.

Mark a route on the chartplotter against which crew can easily compare the ground tack. Discuss how far you are prepared to deviate from this route and how to use XTE to judge this. Update the route regularly to reflect any deviations from course.

If there is any risk of straying into shallow water make sure the helmsman and all crew know which way to turn into the deeper water – instructions should be unambiguous. When sailing under spinnaker, always be ready for a quick drop or gybe.

Halyards should be flaked and ready to run, furling lines ready on winches and snuffer lines separated ready to pull down. If the depth decreases rapidly, give clear instructions about corrective action, try to remain calm and allocate jobs.

If you want to be told the depth, allocate the job to someone who will remain calm and make sure they are close enough to you so shouting is not necessary.