Shark sighting near Australian beach
Police and fisheries officers were notified of the "very large shark" swimming around the end of the jetty about 10.55am.
People flocked to the jetty after news of the sighting spread, with some witnesses claiming it was a great white.
Resident Ercole Lattanzio, who was at the jetty, said the shark was about 3m in length.
"It was a real bluey colour," Mr Lattanzio said.
"I clearly saw one shark, there may have been two, but one was swimming in a northerly direction and it went under the jetty and swam around in circles for about three to four minutes.
"I've never seen a shark that big, that close to shore before."
Witnesses said the shark had attacked crab nets that were dangled from the jetty.
While shark sightings are nothing new to metropolitan beaches, locals were concerned that the shark had been as close as 25m to the shore.
"That is concerning," Mr Lattanzio said.
"This is our local beach, so it's where my kids come to swim, where they would be swimming."
The shark swam around the jetty for about 20 minutes.
Water Operations police were monitoring the area and warnings were issued for swimmers to stay away.
Primary Industries and Resources SA figures show there were almost 60 shark sightings off the state's coast in January and February.
Two weeks ago, a shark was sighted 300m off Largs Bay by the UniSA fixed-wing shark spotter plane.