You observe a vessel displaying two balls in a vertical line at its bow. What is the vessel and what are your obligations?

A. Two black balls in a vertical line indicates a vessel at anchor. A vessel at anchor is not underway. Under Rule 9 and good seamanship, other vessels should keep clear of an anchored vessel. You should plot the anchored vessel and ensure you are passing at a safe distance, taking into account any potential for the anchored vessel to swing to her anchor cable.

B. Two balls in a vertical line indicates a vessel not under command — engines broken down. The vessel may be making way through the water and may not be able to manoeuvre. Give way and pass at maximum possible distance.

C. Two balls in a vertical line is displayed by a vessel constrained by her draught. She has priority over all other vessels except those not under command and vessels restricted in their ability to manoeuvre.

D. Two balls in a vertical line is displayed by a sailing vessel making way under both sail and engine. She is treated as a power-driven vessel under Rule 25.

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