5)

The vessel should be tacked very soon otherwise the vessel will be the wrong side of the islands to be able to enter the channel on the next tack.

This diagram takes time to construct, but it is now very easy to identify the vessel's approximate position and what should be done.The diagram could be left on the chart for future trips.

When the vessel is moving, knowing exactly where you are is not always important, by the time you have plotted it on the chart the vessel is no longer there! It can be better to know quickly where you are approximatelyand leave good margins for error.