Lather up in the shower with your choice of shampoo and rinse. Coat the ends of your hair in conditioner, then rinse with cool water. Squeeze excess water out of your mane with a fluffy bath towel, then pat dry. Don't rub, which can cause knots and frizz.
Grab a can of body-building mousse. If you have thick of coarse hair, you'll need a puff about the size of a tennis ball. Fine or thin hair needs half that. Work it in from roots to ends. Sweep a wide-tooth comb through tresses to distribute mousse evenly and detangle any knots.
Separate hair into three sections. Secure two of the sections with plastic clips. Starting with the loose section, blow-dry hair using a large round brush. When you finish drying the first section, remove the clip on the second section and dry that. Repeat until all of your hair is totally dry; any dampness will make those beachy waves frizzy.
Create Beachy Waves
Wrap a 2-inch section of hair around a curling iron with a 1.25-inch barrel set to medium-high heat. Let the last inch of hair hang out of the iron. Hold the iron vertically, parallel to your scalp, and twist it away from your face. Hold for 10 seconds, then release.
Repeat Step 1 all over your head. The curling iron's 1.25-inch barrel will twirl loose, beach-inspired waves.
Apply hairspray. Use it liberally if your hair is thin -- you need more to hold the wave. For medium to thick or coarse hair, a few shots will lock it in place.