SYDNEY - A dad photographing his 10-year-old son riding the waves on a surfboard also captured a shadowy shape beneath the water that turned out to be a shark, according to reports.

Chris Hasson's 10-year-old son Eden was surfing off Samurai beach, Port Stephens, in eastern Australia, on Tuesday (Jan 24) when the 3m-long creature appeared.

"It was a chance encounter, a one in a million photo," Hasson said, according to CNN.

Concerned for his son's safety, he called for the boy and other surfers to come ashore.

Then he showed them the shot, which they loved, CNN said.

"Everyone was high-fiving after they saw the photo," Hasson said.

Eden even responded with a joke: "Lucky I didn't fall off."

"When I took off, I thought I saw something and when I went to do the first snap off the top I hit something and I thought it was seaweed," the youngster told the Mail online.

"Then when (Dad) called me in I thought it must be a shark because there was a big school of fish we saw.

"If I had known it was a shark in the wave, I would have freaked out and fallen off… I saw the photo and I was shocked."

Mr Hasson, a real estate agent who has surfed all his life, was standing on rocks taking pictures just as Eden glided his board over the creature's head. "I just had a gut feeling so I went into the photos and zoomed in and went 'No way'," he told The Daily Telegraph.

Mr Hasson then called Eden back to shore, yelling "shark!"

He said the terrifying encounter has not deterred his son from returning to the water.

"I look at the image and think, wow, he's lucky he didn't fall off, it would have ended very differently if he did," he said, according to news.com.au..