Three Canadians, including a nine-year-old boy, are safe after being rescued from stormy seas some 450 kilometres off the coast of Hawaii.

The U.S. Coast Guard says two men, aged 29 and 32, and a nine-year-old boy were aboard a sailboat travelling from Puerto Vallarta, Mexico, to Hawaii, when their vessel lost power Tuesday evening in "extreme conditions."

"The vessel reportedly suffered damage to its top forestay and it’s engine overheated," the coast guard said. "The crew attempted to rig a makeshift sail but completely lost its mast in the extreme conditions."

The coast guard then contacted a container ship — the Horizon Reliance — which was 240 kilometres away to come to the rescue of the stranded Canadians. The ship changed direction and travelled at full speed to reach the sailboat, which was adrift in the Pacific.

It reached the area at 1:30 a.m. local time on Wednesday but as the large ship approached, a swell caused the sailboat to capsize and sink, throwing all three Canadians into the sea.

At that point, the ship lowered a ladder into the water and rescued the 29-year-old man from the sea around 2:30 a.m., but the two others, including the child, drifted away.

They were rescued nearly an hour later.

All three Canadians were wearing lifejackets with strobe lights which allowed the rescuers to keep them in sight.

Horizon Lines, the company which owns the container ship, said all three Canadians are in "good health and spirits" and will be medically evaluated and debriefed by the coast guard once they're in Honolulu later today.

"We are thankful the Horizon Reliance was in the right place at the right time to come to the aid of these individuals,” said William A. Hamlin, the company's vice president of operations.

"We commend Captain Kelleher and his crew for their skilled seamanship in accomplishing a successful rescue despite very adverse weather conditions."