Very frustrated with this one. Rhythm kept changing in my head. Don't ask me where it came from, it just sort of ... arrived. Anyway, at least it's out of my head and on the page where it can't get me

I know where you’re sailing. I know these seas well.
All its reefs and currents, tall waves and deep swells.
From the bow of my ship, as we pass in the night,
I sense your confusion, and also all your fright.
And you’re right to hold tight to your rudder tonight,
With sea legs all trembling as you face the long night.
I can see your ship’s course, know the rocks just ahead.
And I’d pay any price, to face them in your stead.
For my ship got its scars from those very same reefs,
Where the wind always blows and the currents run deep.
And I know what I know, and I know what you don’t.
I know what you should do - and I know what you won’t.
For I once sailed those shoals on just such an evening.
No moonlight to steer by makes distance deceiving.
Like you I once trusted in my own eyes and ears,
And knew that no captain ever sailed without fears.
For no sailor’s ventured to places worth sailing,
By turning around at the sinking sun’s failing.
I wish I could warn you of the dangers I know.
But we cannot stop here. We cannot even slow.
More waves always coming, there’s never enough time.
And too great a distance, between your ship and mine.
No advice could help you. You could not read my charts.
Storms are always coming, in spiteful fits and starts.
No good would it do you, the route cannot be taught.
The currents ever tug us, from the courses we plot.
Though you barely see me, I wave as we pass,
May good fortune find you, and your sailing luck last.