A family of three have been rescued from the water off the coast of Halls Head in Mandurah.
A police spokesperson said they were all unharmed.
The boat was left "running circles in the water" before it was retrieved by Mandurah Volunteer Marine Rescue Service and towed back to shore, the spokesperson said.
The incident happened about 3km offshore.
It was reported to Water Police at 11.10am on Wednesday.
It is understood the boat tipped over and the family fell overboard into the water.