What are the umpire's main duties?

Under Rule 12.5, the umpire:

• Safety and fairness: decides whether the wind or water is likely to make the race unsafe or unfair, and acts to make it safe and fair. In bad weather, the umpire decides whether a race may start, continue or must be stopped.
• Start: makes sure, with the aligner, that the correct starting procedure is followed, and starts the race by dropping the red flag.
• Conduct of the race: makes sure no crew gains an unfair advantage or suffers a disadvantage from opponents or outside interference. If a crew is impeded, its chance of winning must be fully restored.
• Penalties: imposes appropriate penalties on crews at fault, in principle only after a warning.
• Steering: gives no steering instructions except to avoid accidents or stop crews being impeded by their opponents.
• Stopping and re-rows: may stop the race, penalise and order a re-row, now or later (setting the new time with the President of the Jury). Alternatively, may let the race run and exclude crews afterwards. May decline a re-row if the impediment didn't significantly affect the result.
• Launch: keeps the launch well placed and keeps its wash off crews.
• Medical information: receives from control commission any rower medical conditions that the club representative has declared.

All officials share the overriding duty to keep rowers safe and to apply the Rules of Racing consistently (Rule 12.1).