1,000 balloons were released from a barge on the Thames near London Bridge during Friday morning's rush hour to promote the launch of a new firm offering speedboat excursions.
The biodegradable balloons each carry a voucher offering a free trip on a RIB Tours London high-speed sightseeing tour.
RIB Tours London, based at Festival Pier on the South Bank, is run by Robert Cairns and John Williams.
Both partners have the Thames in their blood: the two men served as apprentices to their fathers before becoming qualified Thames watermen in their own right.
Nine years ago they launched London Party Boats and have now teamed up to form RIB Tours London.
Since London RIB Voyages was founded in 2006 a number of firms have sprung up offering high-speed rides in rigid inflatable boats (RIBs) on the River Thames.
RIB Tours London offers a 50-minute round trip from Festival Pier to Canary Wharf with adult tickets priced at £29.99 – although the route can be varied to suit the group.
• Balloon releases are now discouraged by many organisations because of their impact on wildlife and the environment. The Marine Conservation Society, the Royal Society for the Prevention of Cruelty to Animals, the Tidy Britain Group and the National Farmers Union are among the organisations that have expressed concern about the practice.