Why would you unload by a human chain, why not use dollies? Think it was better optics?
cause they have bore bodies than carts...
and carts have to go back AND forth, chain only has to go one way
Because that is the fastest way short of a crane to/from the deck to load/unload on a ship. Even then it would require a chain to move it to the deck. That is coming from an interior space with multiple watertight doors and hatches that are not wheel friendly.