Cottesloe Beach, in the early morning, is a favourite of mine during the summer months, although other beaches would probably be just as nice. Otherwise, it's also nice at Kings Park or any of the riverside parks.
I've only had a week's stay in WA, so I was going to mention Kings Park may be a good place to meditate. I'd love to visit Cottesloe beach, & see the sculpture by the Sea, (or SxS.) I don't think there's as many pieces as the Bondi to Turramurra 1 the we visit each year, (about 105) & I take about 110 photos! Ops, I'm way of the subject again.