Swimmers were evacuated from the water at Boomer Beach late this morning after a 3m shark was spotted about 20m offshore.

The shark was spotted by the fixed-wing shark patrol plane which then circled the area and sounded a siren.

Aerial patrols are carried out from North Haven to Rapid Head and from Rosetta Head (The Bluff) to the Murray Mouth each day of the school holidays.

A shark was also spotted at Port Willunga yesterday just after 2pm. 

A large Bronze Whaler was also reported near Middleton Point at about 3.30pm.