I would doubt the 'just off the boat' connotation for the origins of navvie, the acts of parliament which were required for the creation, or closure, of a canal described them as inland navigations, and navigation and then cut seem to have preceeded the term canal.

From the canals it was logical for the workers to go on to the building of railways, and then the highways and motorways as cars became the next big thing.

Navvies must have seemed like visitations from Hell for a quiet village, as the canal or railway 'head' approached there would have been people arriving to find food, drink, building materials - setting up a shanty town and then the workers themselves, typically described as dirty foul mouthed ungodly people, plus all the hangers on, and families.

Once the work was finished and the boats or trains were running it must have seemed that the village would never be the same again.

Anne