Summer is murder on stick-straight hair -- humidity is the enemy of sleekness, and heat leads to a general dryness and lack of shine. So rather than fight the elements, beachy bedhead waves allow celebs to be artfully disheveled and messy on purpose.

The "I just woke up" look can be styled in a variety of ways, like Olivia Wilde's defined semi-curls or Selena Gomez's tumbling tendrils.

Olivia Wilde:

The former 'House' actress wore her golden ombre locks in a defined tangle of curls and waves that may have looked effortless, but rest assured her stylist likely created each strand with a curling iron (and product) -- so this probably took some time.

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Selena Gomez:

Gomez's mega-long, face-framing extensions were rich, thick and shiny, with the kind of waves that look like she slept with her hair in loose, damp braids, woke up, shook 'em out and went about her day. This style is simple to recreate and adds killer body and fullness.

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Britney Spears:

Brit Brit's beachy hair isn't so much waves as it is shaggy, tossed around and artfully messy, created with a little product raked through the hair. It's unpolished, but it works. Girls with layers can rock this look with ease.

Jason Merritt, Getty Images

Victoria Beckham:

The mom of four, fashionista and former Spice Girl is usually pulled together and prim, so this tangle of messy but glossy waves on one shoulder was a flirtatious and fun change of pace.

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Jennifer Lopez:

J. Lo's sunkissed, thick and textured waves -- likely created with a sea salt spray -- sacrificed gloss and shine for a dirty, roughed up "I spent all day on the beach" look.

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