Don’t be alarmed by what may appear to be a ferry accident in Hingham early Sunday — it’s just a drill. At 7 a.m., public officials will practice what to do in the event that a commuter ferry crashes into a dock and injures more than a dozen passengers, according to a statement from the Massachusetts Department of Transportation. Firefighters, police, and other emergency workers from Hingham and surrounding towns will conduct the mock rescue of approximately 40 people volunteering to act as ferry commuters in various states of distress, said Randy Clarke, senior director of security and emergency management for the Massachusetts Bay Transportation Authority and MassDOT. The drill will take place at a commuter boat dock at 18 Shipyard Drive. Clarke said the MBTA, which organizes the drill as part of its emergency preparedness program, has not conducted an exercise involving ferries in at least five years.