RedactedNarrative: Vessel 1 had backed out of its slip and turned to port.  Vessel 2 was docked 2 slips east of the slip Vessel 1 had backed out of.  While turning and going forward, Vessel 1''s starboard-side stern corner struck Vessel 2''s swim-deck on the portside stern-most corner.  That contact pushed Vessel 2 hard enough that it was shoved into the houseboat it was tied to and disturbed that houseboat enough that all occupants inside took note.