The ducks were released near Hampton Court Palace as part of the Great British Duck Race, raising money for charities including the NSPCC and WaterAid.
Official entrants were an exotic blue, instead of the more traditional yellow, after stewards last year face problems with people throwing their own unofficial plastic birds into the water at the event.
The 250,000 ducks created a world record this year for the most plastic ducks raced together. It beat the record set on the Thames last year, when 165,000 were raced down stream, raising more than £100,000 for charity.
Each duck cost £2 to enter in to the race, with the owner of the first past the finishing line at the Sheriff Boat Club at Albany Reach receiving a £10,000 first prize.
In 1992, 29,000 rubber ducks fell overboard from a boat in the Pacific Ocean and floated around the world for more than 15 years.