Re: Forces on a dockline while docking....
People ferries and water taxis use a similar technique when they make their quick unload/reload stops.. Usually in fwd gear and the rudder turned away from the dock.. Thay basically motor against the spring line holding themselves on the dock.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)