At least 12 people were in critical condition, and many others suffered minor injuries, Fire Chief Harold Scoggins said.
There was no immediate word about the cause of the crash, which involved a military-style tour bus that can also be operated on water. Initial reports described the accident as a head-on collision.
A driver who was behind the duck boat said the tour bus and duck boat were headed in opposite directions.
Witnesses described hearing a loud screech and then seeing injured people lying on the pavement or wandering around in a daze.

The amphibious vehicle is operated by a tour company called Ride the Ducks, which offers tours that are known for exuberant drivers and guides who play loud music and quack through speakers as they lead tourists around the city.
Company President Brian Tracey called the fatal accident 'devastating' and said that the company continually trains and conducts ongoing education classes to ensure safety.


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