The Victorian Fisheries Authority confirmed a shark was reported to have nudged the surfer about 100 metres from shore, at Logan's Beach at 9am.

The surfer returned to the shore and Local Fisheries Officers investigated the water to see if they could sight the shark or if there was anything luring the shark into the area.

The Warrnambool incident comes after a confirmed sighting of a shark estimated to be more than four metres long at Port Campbell on November 27.

Port Campbell resident Simon Illingworth said he was watching a group of surfers when they began paddling fast towards the shore.

"It became pretty obvious there was a shark sighting and I did see a splash not far from them," Mr Illingworth said.

"We went down to the beach and some of the surfers were off-duty surf lifesavers and they said it was a Great White about 14-foot-long."

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Mr Illingworth said the surfers were relieved to be back on land but shark sightings were not a reason for people to stop swimming or surfing.

"Everyone knows there's big sharks around and you see less than one per cent of them," he said.

"We don't have a lot of sharks down here and I would be really disappointed if people thought they shouldn't swim in the ocean."

The Victorian Fisheries Authority said shark attacks in Victoria were uncommon and there had been no fatalities in Victoria for more than 30 years.