Question 1

When heaving up the anchor, what is meant by the "critical period" and "critical instant"?

Accepted Answer

The critical period is the time during weighing anchor when the anchor has broken out of the seabed but is not yet clear of the bottom, and the critical instant is the moment the anchor leaves the bottom — during this period the vessel is most vulnerable to being affected by wind/current with reduced ability to manoeuvre safely During anchor recovery, the "critical period" is the phase after the anchor has broken free of the seabed's holding ground but before it is fully aweigh (clear of the bottom) — the vessel is no longer held by the anchor but is not yet free to manoeuvre normally, making it vulnerable to drifting under wind or current effects, particularly in confined waters. The "critical instant" is the specific moment the anchor leaves the bottom (anchor aweigh). Good bridge teamwork and awareness of these moments are important for maintaining control of the vessel's position during the weighing operation.

Question 2

You're preparing a passage plan for a coastal leg in a yacht drawing 3.2m. At one point the chart shows a least depth of 3.8m at chart datum. What MUST you check before finalising this leg?

Accepted Answer

The tidal height at the time of transit to confirm sufficient under-keel clearance Charted depths are referenced to chart datum (often LAT), so you must add the predicted tidal height for your transit time to get the actual depth, then compare to your draft plus a safety margin to confirm UKC.

Question 3

During your watch the ECDIS gives a "safety contour crossing" alarm. What is the correct response?

Accepted Answer

Assess the situation against the planned route and charted depths, take action to maintain safe water, and inform the Master if there is any doubt A safety contour alarm indicates the vessel may be approaching water shallower than the set safety contour. It must be investigated against the route and charted information, with avoiding action taken and the Master informed as appropriate — never simply silenced.