The traditional melody that Annie McLeod collected, and adapted, and for which Harold Boulton and she most probably co-wrote the words, was, perhaps, not a shanty, but an 'iorram'

"Of uncertain etymological origin, the word shanty emerged in the mid-19th century in reference to an appreciably distinct genre of work song, developed especially in American-style merchant vessels that had come to prominence in the decades prior to the American Civil War."

https://en.wikipedia.org/wiki/Sea_shanty

(chanty is probably linked to the french word for sing, you might imagine)


"The iorram (pronounced-irram) or rowing songs were sung in ¾ or a slow 6/8 time. The 1st beat is very pronounced and corresponds with lifting the oars out and swinging them forward, 2 and 3 are the pulling stroke. Some of these airs were or still in use as waltzes in the Western Isles.”

http://chrsouchon.free.fr/skyeboat.htm

If you're looking to generate a 'best quality historic and contemporary interpretation' of the song, here are some textual and lyrical variants to consider.


Chorus:
Onward / "Onward"
skye / Skye


Verse 1
Thunder clouds / Thunder claps
foes's / foes
stand on / stand by

Verse 2
weary / royal
royal / weary

So the full words, with suggested amendments, would go something like:

Speed bonnie boat,
Like a bird on the wing.
"Onward" the sailors cry.
Carry the lad
That's born to be king
Over the sea to Skye.

Loud the wind howls,
Loud the waves roar,
Thunder claps rend the air.
Baffled, our foes
Stand on the shore.
Follow they will not dare.

Speed bonnie boat...

Though the waves leap,
Soft shall ye sleep
Ocean's a weary bed
Rocked in the deep
Flora will keep
Watch by your royal head

Speed bonnie boat...

Many's the lad
Fought on that day,
Well the claymore could wield.
When the night came,
Silently lay
Dead on Culloden's field.

Speed bonnie boat...

Burned are our homes,
Exile and death
Scatter the loyal men.
Yet, e'er the sword
Cool in the sheath,
Charlie will come again.

Speed bonnie boat...