What are the Umpire's duties before and during a race?

Rule 98 says the Umpire ensures the proper conduct of the race and the safety of the rowers, and endeavours to ensure that no crew gains an advantage or suffers a disadvantage from its opponents or outside interference. Under Appendix 13:

• Precedence: except for their own specific duties, the Starter and the Judge at the Start are subordinate to the Umpire.
• On the way to the start: inspect the course installations, check there are no obstacles or wash from motor boats on the course, and check crews on the water follow the traffic rules. Defects go to the President of the Jury (by radio if needed) and to any crews concerned.
• During the start: the launch is in principle beside the Judge at the Start or behind the crews in the centre of the course. If the start is faulty for a reason other than a false start (which is the Judge at the Start's call alone), the Umpire may order the Starter to stop the race or stop it by ringing a bell and waving the red flag.
• During the race: follow the crews down the centre of the course, position the launch to act effectively, and make sure crews they want to address can hear them. Avoid hampering crews with the launch's wash.
• Type of race: the decision may take into account whether it is a heat, repechage, quarter-final, semi-final or final.
• Steering indications: not given, except to avoid accidents or stop interference by opponents (Rule 98.2).
• Coaching devices: check the area beside the course regularly, because coaching with electric, electronic or other technical devices is not allowed during racing.
• Dress: stand upright in the launch and wear the prescribed clothing.
• Zonal umpiring: at RA events the Technical Delegate may advise that some races are umpired from stationary boats, or from the land beside the course. The President of the Jury designates where umpires are positioned, and zonal umpires keep in radio contact with each other and the President.