West Australian police are urging beachgoers to keep their valuables safe this summer, with a particular warning to those who use navigation devices.

Officers patrolled Scarborough and Cottesloe beaches this morning and checked whether people had kept items such as mobile phones on them or left them in vehicles.

Acting Senior Sergeant Chris Martin said the patrols were part of WA Police's Operation Celsius crime strategy targeting volume crime in the metropolitan region.

Police launched the operation in December as a pre-emptive measure against the traditional summer surge in crime.

Acting Senior Sergeant Martin said some people had still not heeded the message to keep their belongings safe.

"Within 15 to 20 minutes, we did a walk through a carpark and we located several Navmans, radar detectors, cameras and a purse just left on a seat in the car," he said.

"We've also located a car that was unlocked and one that was with windows down."

Police said beachgoers need to keep an eye on their belongings. ( ABC News: Hayley Roman )

He said navigation devices in particular posed a risk because owners usually programmed in their home location.

"If they leave their keys down at the beach sand, the offenders will grab the keys off the beach, walk up to the car park, find which car the keys belong to, they'll have access to that Navman, press that home button and now they've got keys and the location where those keys can be utilised and burglaries committed."

He said while criminals were ultimately responsible for their crimes, police and the public had a joint responsibility to reduce opportunity.

"Whilst you're out and about, just maintain an eye on your belongings and keep it within a close range so you can access if someone is looking at it."