Annual 22-mile race on the Thames from Greenwich to Richmond featuring approximately 300 craft.
Any traditional-style, coxed boat, propelled by a minimum of four oars or paddles, without sliding seats or riggers, may take part.
Each boat is computer-handicapped according to its potential performance, so everyone has an equal chance in this 'slowest away first, fastest last' handicap race.
Every year brings a new and unusual boat to test the handicappers.
This year's official charity is MediCinema which provides cinemas in hospitals around the UK.
There will be disruption to Thames Clippers boat services whilst the race is under way.
Related website: www.greatriverrace.co.uk