Shanty, like calypso, is performed extempore:

"...the men sang a verse, or part of a verse, and were then followed by the females, who took up their part very readily; and their fine clear voices, keeping time with the motion of the oars, had a pleasing effect."

A rose is a rose is a rose...

Same volume (and crew) has the earliest example of Cheerly Men in the document record.

If the object of a good rowing, pump or capstan cadence is to "fool the hours" I'd say these folks here have got the general idea just fine.