The most popular nudist beach is at North Swanbourne. It is between Cottesloe and City Beaches. Past the carpark is a sign warning a clothing optional beach is ahead. The sand is clean with plenty of rubbish bins around. It is a safe beach.
There's a section of Warnbro beach near Rockingham that is still designated as a 'free' beach. Based on a bit of local opposition to this nudist haven, this might not stay as a free beach for much longer.