Given that modern vessels rely primarily on GNSS, why does the OOW Unlimited syllabus still require a working knowledge of celestial navigation?

A. It is purely a historical formality with no genuine operational relevance

B. It is tested only for engineering officers, not deck officers

C. It is required only for vessels without an ECDIS fitted

D. Celestial navigation provides a genuinely independent position-fixing method with no reliance on any electronic system, satellite signal, or shore infrastructure — making it the ultimate fallback if GNSS is lost, jammed, spoofed, or its integrity cannot be trusted, particularly on ocean passages far from other fixing aids

A. The tidal height at the time of transit to confirm sufficient under-keel clearance

B. The yacht's fuel consumption for that leg

C. The colour of the seabed shown on the chart

D. Only the distance to the next waypoint

A. 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

B. Ignore it — ECDIS alarms are frequently false and can be left running

C. Switch the ECDIS to standby mode and navigate by GPS position alone

D. Acknowledge and silence the alarm immediately so it does not distract the helmsman