There are some girls who just look better with tousled hair, rather than perfectly straightened, flat-ironed hair and Sienna Miller is one of them. Kate Hudson is another, Jessica Simpson yet another.
To get the beachy, wavy look it helps if your hair has some natural wave to it and this look works on hair of almost any length, even chin-length hair or a bit shorter. For a quick beachy look, let hair air dry, scrunching it as it dries. Once dry, twist pieces around your fingers to create "ropes." Spritz each rope with hairspray.
If you have straight hair, you can get this look with a curly iron and some salt spray. See How to Get Beachy, Sexy Waves for directions.
Photo: Sienna Miller by Andrew H. Walker, Getty Images