A young surfer has told of his terror as he realised a shark had grabbed his foot and knocked him off his board in South Australia.

Oliver Tokic-Bensley, 16, said he was surfing by himself in murky water off the tourist town of Middleton was he was struck.

He was about 100 metres offshore, frantically paddling in, hoping the shark wouldn’t strike again.

A young surfer has told of his terror as he realised a shark had grabbed his foot and knocked him off his board in South Australia. (9News)

“(I was) sitting on my board waiting for a wave to come and something just came and grabbed my foot,” he said.

“I fell into the water with it and then maybe five metres in front of me there was a little fin that popped up, and I just hopped on my board and legged it back to the beach.”

When the fin disappeared below the surface, Oliver faced every surfer’s worst nightmare, not knowing if the predator would strike again.

“It was pretty frantic,” he said.

“There were no waves to catch at the time it got me so I just had to paddle.”

His father, Andrew Bensley, had been watching his son from their holiday home but didn’t see the attack.

When Oliver finally made it to shore and reached his phone he called his sister to raise the alarm. (9News)

“I think the movement of his foot and maybe the murky water, the shark mistimed the hit. If it was a little bit up he definitely would have lost his foot,” he said.

“Based on the size of the teeth it was a reasonable-sized shark.”

When Oliver finally made it to shore and reached his phone he called his sister to raise the alarm.

“I just said ‘I just got attacked by a shark’. I didn’t word it very well so she thought it was a lot worse than it was. So she sort of started stressing out,” he said.

While Oliver has quite the tale to tell – he says the attack won’t keep him out of the water.

Oliver Tokic-Bensley, 16, said he was surfing by himself in murky water off the tourist town of Middleton was he was struck. (9News)

He’s planning to be out catching waves again as soon as his foot is healed.

“He said to me, ‘the chances of getting attacked by a shark is one in 3 million and what are the chances of getting attacked twice right?'” Bensley said.

Judging by the colour of the fin, Oliver believes the shark might have been a bronze whaler, which struck his foot about 4.30pm on Good Friday.

“We were talking around having a religious presence in your life and I said ‘your guardian angel’s definitely working overtime for you today,” his father said.