RedactedNarrative: The Operator of Vessel 1 reported that Vessel 1 slowed due to a loss of wind.  A large wind gust then came up, snapping the mainline on the main boom.  As a result, Vessel 1 capsized.  An Occupant aboard Vessel 1 was struck on the top of the head by the boom during the capsizing.  Emergency services responded and released the Occupant (Victim) at the scene for a bruise on hte top of the head.