How Can This Happen?

A lot of people don't realize a tanker with a single screw will maneuver pretty well on its anchor and a shot or so of chain (a shot is equal to 15 fathoms or 90'). While small boat owners are inclined to think this poses a danger to the vessel's propeller, ship captains remind us that large oil tankers are hundreds of feet long. All they're doing is dropping the anchor in the mud under the bow, using it as a break or drag against the force of the screw.

I can't say this is what happened to the tug in the video above but it's likely an order was given to drop the anchor for maneuvering not realizing the tug was in position under the hawse pipe.