All I know is that this song was about them [not Scottish, by the way]
As aa cam' thro' Sandgate,
Thro' Sandgate, thro' Sandgate,
As aa cam' thro' Sandgate'
Aa heard a lassie sing:
Weel may the keel row,
The keel row, the keel row
Weel may the keel row
That ma laddie's in.
But, probably they were involved in barge transport of coal.