New regulations have been introduced to restrict the speed of commuter and tourist boats on the River Thames.
Commuters use high-speed catamaran services
A recent increase in the number of fast vessels on the river prompted the move by the Port of London Authority (PLA).
Passenger vessels operating in the vicinity of Greenwich and in central London are now restricted to a maximum speed of 12 knots.
The PLA said it was necessary to bring in the regulations to ensure "continued high safety standards".
Safety is paramount
"We have made this precautionary move because of a significant increase in the number of fast vessels on the Thames," said a PLA spokesman.
He said more high-speed boats had begun operating on new routes and leisure operators had introduced new tourist related high-speed trips.
Thames Clippers, which operates a fleet of 10 passenger boats, said their vessels operated at an average speed of between 10-12 knots in the areas affected.
Sean Collins, from the firm, said: "When there is a lot of movement we have got to ensure safety is paramount."
He said as long as the limit only applied to central London and they were able to reach speeds of between 24-29 knots on longer journeys then the service was "totally safe."