Aerial shark patrols along Adelaide and south coast beaches stared on the weekend, two weeks earlier than planned.

The early start follows an attack at Port Noarlunga on Friday 10 November, which left a 32-year-old woman with serious injuries.

The patrols started on Saturday 18 November along two stretches of the coastline – from Victor Harbor to the Murray Mouth and from Rapid Bay to North Haven.

They usually start in the first week of December, operating in South Australia since 2003.

The shark patrol flights will operate daily until Easter over metropolitan beaches, with flights to be extended to the south coast on weekends, school and public holidays.

The fixed-wing aircraft have the words ‘shark patrol’ in large letters on the underside and are fitted with a siren to warn beachgoers.

State Emergency Service Chief Officer Chris Beattie says swimmers should take heed of any warnings from patrol aircraft.

"In the event of a sighting that may pose a risk to the public, the aircraft will fly continuous orbits over the area and sound the siren, at which time people should immediately leave the water," he says.