The helicopter was in the area investigating a report made to Water Police this morning by a couple who said a shark of that size had lunged at their daschund cross at the dog beach, west of the estuary entrance.

Mandurah Fisheries and Marine officers have a vessel in the area, but they

haven't been able to locate the shark and the helicopter has since lost sight of it.

To be cautious all water users in the area have been advised to remain alert at all times.

All shark sightings should be reported to Water Police on 9442 8600.