What are the 'safety contour' and 'safety depth' settings in ECDIS, and why must the OOW actively set them rather than rely on default values?

A. They are fixed international standard values that never change between vessels

B. The safety contour is the depth contour ECDIS treats as the boundary of safe water for that vessel (used to trigger grounding-related alarms), and the safety depth similarly affects how soundings are displayed/highlighted — both must be set based on the vessel's actual draught, planned under-keel clearance margin, and passage conditions, since an incorrect or default setting can mean the alarm system is not actually protecting against the vessel's real grounding risk

C. These settings only affect the colour scheme of the display, with no bearing on alarms

D. They are set once at ECDIS installation and never need adjusting for different passages

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

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

C. 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

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