The Blackwood River estuary is one of the best flat water kite/windsurfing spots in WA. The river mouth has a long sandbar before the river opens to the sea, the stretch of water behind the sand hills is great for beginners. The water is clear and shallow, kites sail a little better than windsurfers as they reach above the sand hills. Plenty of room and easy access to the water.
Cheers
Bob Dunlop