Aerial shark patrols have started two weeks early this year following an attack at Port Noarlunga last week.

The incident, which left a 32-year-old with serious injuries, was the fourth this year in South Australian waters, with two fatalities.

Swimmers on two stretches of coast – between North Haven and Rapid Bay and between Victor Harbor and the Murray Mouth – will start to see the shark-spotting planes from November 18.

Traditionally, the patrols have started in the first week of December.

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

The fixed-wing aircraft, which have the words “shark patrol” in large letters on the underside and are fitted with a siren to warn beachgoers, have operated in South Australia since 2003.

State Emergency Service Chief Officer Chris Beattie said 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," Mr Beattie said.

The State Government provides more than $460,000 each summer for the shark patrol program.