The 40-year-old Fingal Bay resident, who paddles the area most days, was moving through the spit about 8am when the shark's head and jaws emerged from the water and tore into the ski near where he was sitting.

"It came out of nowhere, rammed the ski catapulting me into the water," Mr Milne said.

"It was angry and I was really petrified."

Mr Milne said he grabbed his paddle and scrambled back onto the now-damaged ski and made it safety to the outer island shore.

He never saw the shark again.

The damage to his $2500 racing ski included a split down the side.

Mr Milne said he spent about 10 minutes "calming down" on the beach before deciding he would have to go back onto the ski and paddle home even though it was taking water.

"The only other option was to swim across the spit and I wasn't going to do that," he said.

"This has been a bit of a wake-up call for me. I'm just glad I've still got all my limbs."

He believed the shark was a bull variety between two and three metres long and would probably have been there chasing mullet.