Mandurah is a car city with one significant exception: the railway that reaches central Perth in under an hour. How much you use each one shapes where you should live.
The Mandurah line
The train runs from the city centre to the Perth CBD in around fifty minutes, with park-and-ride at the stations along the corridor. It is what makes a Perth job while living on the coast workable — and the single biggest reason to weight your suburb search towards the rail corridor if the capital is part of your plan.
Roads and the everyday
Off the rail line, Mandurah runs on cars. The Kwinana Freeway and Forrest Highway carry you north to Perth and south into the South West, and getting around town is a fifteen-to-twenty-minute affair rather than a commute. The rebuilt foreshore and marina are walkable; most of the rest of the city is not, which is worth planning for if you would rather not run two cars.
A car city with a fast train to the capital. If you will use Perth often, live near the line; if not, the coast opens up.