A teenager is being hailed as a hero after safely halting an unmanned boat that was careening in circles on Lake Winnipesaukee, New Hampshire's largest lake.

GILFORD, N.H. (AP) — A runaway boat, unmanned and speeding in circles on Lake Winnipesaukee, was brought to a safe stop by a teenager who leapt onto it from a personal watercraft.

Rich Bono, who recorded the incident, recounted being on the dock at Smith Cove on Wednesday when he heard a commotion in what is typically a tranquil, no-wake zone.

"I heard the engine revving and looked down towards the noise. I saw a boat circling, circling, circling, with no one aboard," he said. "Clearly, that's not good."

Bono later learned that the boat's operator, a sailing instructor, had leaned into the water to retrieve a tennis ball used in lessons when a student's sailboat capsized. The sailboat's mast accidentally hit the motorboat's throttle, ejecting the instructor and setting the boat into a spin.

Seventeen-year-old Brady Procon jumped onto his neighbour's personal watercraft. They approached the runaway boat, and Procon leapt aboard, successfully shutting down the engine. Brady was a hero," Bono emphasized in a Monday interview.

Despite multiple children in sailboats and other vessels nearby, there were no injuries or property damage, Bono confirmed.

That boat was running at full throttle," he noted. "Boat motors are dangerous; they're not forgiving if someone gets hit.

Procon, who plans to join the U.S. Navy in the fall, described the experience to WMUR-TV as both frightening and exhilarating. It was scary but also kind of fun," he remarked. "I would do it again.