Eight tourists on a "duck tour" pleasure boat trip were rescued by a lifeboat after the amphibious craft began to take on water near Lambeth Bridge.
The passengers, including a girl of five, were near Lambeth Bridge when the engines failed and the vessel drifted into a moored boat.
The craft became pinned and began to list. The passengers and two crew had to climb out of the portholes.
London Duck Tours introduced the yellow fleet – originally using the Frog Tours name – in 2000. Tours depart from County Hall on the South Bank and the amphibious vehicles enter the water near the MI6 building on Albert Embankment.
The Port of London Authority is investigating the incident.