A more thorough explanation:

Navagium

Navagium is a word from Latin that means "ship" or "voyage". In the past, it was also a duty that a tenant had to transport the lord's goods by ship.

For example, if a lord had goods that needed to be transported across the sea, they would require their tenant to fulfill their navagium duty by providing a ship and crew to transport the goods safely. This was an important duty because it ensured that the lord's goods were transported safely and efficiently.