PARIS - It looks like a bus that has taken a wrong turning, speeding down a slipway into the River Seine, scattering swans and prompting screams from the passengers. But when the splash subsides, the bus floats serenely along the river.

Welcome to one of the French capital's newest tourist attractions: an amphibious bus that drives along the city streets, and then converts instantly into a river-going pleasure boat.

"It was very different from the usual," said Giulia Gallo, a 12-year-old girl from Italy on board the bus this week. "But it was very nice."

Amphibious tour buses -- commonly known as ducks -- have been used for years to ferry tourists around other cities in the world. They are often modified military sea-borne assault craft. Some have made headlines by sinking, or catching fire.

But the version in use in Paris is a new purpose-built design constructed largely in France, and, according to its operators, it is the first amphibious vehicle to gain a license to carry tourists on the roads and waterways of Paris.

The tours have been run since this summer by a firm called "Canards de Paris", French for ducks of Paris.

On an excursion this week, the vehicle in conventional bus mode carried passengers past sights including the Arc de Triomphe and the Eiffel Tower.

Later, the bus switched to boat mode, engaging its propeller at the rear to float along the River Seine. Life vests were suspended from the ceiling, and an anchor was stowed in a box on the side of the bus.

Marcel Pinault, an 8-year-old from a suburb near Paris who was on the bus with his mother, said it was "very different from other boats, and other buses. It's a mix of both."

(Writing by Christian Lowe; editing by Philippa Fletcher) ((christian.lowe@thomsonreuters.com; +33 1 49 49 52 07;))