An Aussie teenager who posted a selfie of his close-up encounter with a shark while surfing has admitted it was a hoax.

Alex Hayes, 17, told Mashable Australia he thought it “obvious” the photo was not real.

“I would be happy to have a cruisey, chiller of a shark as a buddy,” he wrote in an email. “And because that is unlikely, I simply made one with the add of some humour!”

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He said he used Photoshop to mock up the scary meeting.

Before the hoax was revealed, Mr Hayes said he was first freaked out when he saw the shark but then he realised the “bad boy” was really “a chiller and just cruisin”.

The photo that looks too close for comfort was posted to Instagram where it’s generated thousands of likes and comments from astounded viewers.

“Luckily I brought my gopro, otherwise no one would have believed me… Changes my perspective about sharks – they aren’t all dangerous!” he wrote.

Mr Hayes said he was having a break while floating on his board when he noticed the shark behind him.

While the post went viral, news website The Inuisitr said people were questioning just how genuine the photo was.

Skeptics pointed to a previously forged image of a shark from a boat, saying that the two creatures look suspiciously similar.

Turns out they were right all along.

“It was a harmless joke,” he said. “And everyone got entertainment from it so I’m happy! No harm done!”