Forty minutes south of Essaouira by bus is Sidi Kaouki, with its great beach. You can get here on a taxi or on the local bus (ask the tourist office for the time table and for the stops).
The beach is very famous Among wind surfers for its strong winds. If you are into tanning, the wind may ruin your beach day. Nevertheless you can always go to one of the beach restaurants and enjoy a great meal.
Locals also rent camels for an hour.