You are on watch and are identified as the stand-on vessel under Rule 15 (crossing situation). Describe your obligations under Rules 16 and 17 and at what point the stand-on vessel may take independent action.

A. The stand-on vessel under Rule 17(a) must maintain course and speed and may take avoiding action only if the give-way vessel fails to act (Rule 17(b)). Rule 17(b): the stand-on vessel MAY take action when it becomes apparent the give-way vessel is not taking appropriate action. Rule 17(b) action must NOT be an alteration to port for a vessel on your port bow. Rule 17(c): when collision cannot be avoided by the give-way vessel alone, the stand-on vessel SHALL take such action as will best aid to avoid collision.

B. The stand-on vessel must maintain course and speed at all times. Only the give-way vessel may take action. The stand-on vessel should sound a signal and await action by the give-way vessel.

C. Rule 17 permits the stand-on vessel to alter course at any time provided it signals its intention on the whistle with one short blast for starboard and two for port.

D. The stand-on vessel may take action under Rule 17 only when the vessels are less than 0.5 nautical miles apart. Before that range the stand-on vessel must maintain course and speed regardless.

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