Question 1

You're OOW on watch in an area where the atmosphere is stable — any rising air cools faster than its surroundings and sinks back down. Which weather pattern would you expect to develop under these conditions?

Accepted Answer

Smooth air with poor vertical mixing, layered stratus-type cloud, and a risk of fog or haze, with at most light precipitation A stable atmosphere actively resists vertical motion, so any turbulence or convective cloud is suppressed. Instead you get smooth air, poor vertical mixing (a common cause of fog and haze building up near the surface, since pollutants and moisture cannot disperse upward), and cloud that spreads out in flat layers rather than towering upward — with precipitation, if any, staying light.

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.