DEERFIELD BEACH, Fla. -- A man dashing across a lake on a customized personal watercraft at about 55 mph was killed in an apparent collision with a flying duck.

Leon Resnick, an employee of Riva Yamaha, was testing the water jet-propelled craft Thursday on a lake about 20 miles north of Fort Lauderdale, investigators said Monday.

A co-worker who was watching turned to pick up a radar gun to check Resnick's speed, and when he turned back Resnick was no longer aboard the craft.

Resnick, 31, of Hollywood, died of a blow to his head, the Broward County medical examiner's office said.

"Our theory is that the bird was airborne and clocked him in the head," said David Bamdas, an owner of the dealership.

At the speed Resnick was traveling, the 10- to 15-pound duck "might as well have been a cinder block," Bamdas said.

The bird's carcass was found nearby and there were feathers on the water bike's handlebars, said Broward County sheriff's spokesman Hugh Graf.