David Sheridan, 42, was riding his kiteboard while lurking in the water, just a few feet below, was a whale.
As the New South Wales man surfed, suspended beneath a large kite, the whale smacked him on the back of the head with its tail.
"It all happened so fast that all I could do was crouch down as the whale swam under me," Sheridan told Sydney's Daily Telegraph.
"I saw the huge shape, and my reaction was to duck while remaining attached to the flying lines from the sail above me."
"The next thing I felt was its tail come up and hit me on the back of the head."
"I honestly thought I was gone – it was such a forceful blow – but then the whale eased off, and I was able to sail away."
"But my legs were really shaking. I've never been through anything like that before and probably never will again."
Sheridan's camera was attached to the kite and programmed to take photos every ten seconds.
He was kiteboarding near Valla Beach, off the north coast of New South Wales, with two friends.
"The camera was set to start firing off shots every 10 seconds as soon as I hit the water."
"When the sail was at full height, the camera was about 25m above the surface. It was a lucky shot to snap the whale as it came up underneath me".
"It would have been great to have got a picture a second later when the tail came up and hit me in the back of the head, but you take what you get."
"It was more of a push than a punch. I expected more."
Source: Telegraph