Shark encounter makes boaties cautious

Four friends are not keen on dangling their feet over the side of their boat again after a hungry shark attacked their outboard motor as they fished off Hawkes Bay.

Bry Mossman said a three-metre mako shark circled their aluminium boat for about 30 minutes before it attacked their outboard motor as they fished.

The attack did not damage the boat but left teeth indentations in the motor, she told the New Zealand Herald.

Mrs Mossman said it disappeared only after her husband David gave it a couple of bangs on the nose with a boathook.

"We saw the teeth coming for us following fish we had caught -- then it hit the boat and swerved to the side," she said.

"It circled for about half an hour and was lifting its head looking at us as it was swirling behind the boat, then it started to attack the motor."

It was more interested in the boat than the blue cod they threw it, she said.

It was believed sharks were attracted to outboard motors because of the small electric field they set up in the water which was similar to shark prey.

Department of Conservation shark expert Clinton Duffy said metal in seawater reacted with salt ions to produce an electric field sharks often mistook for prey.

Metal boats and outboard motors often used a sacrificial anode to prevent corrosion in seawater and the electric field it created would have attracted the shark, Mr Duffy told the Herald.