Gisele is out of this world, and so is her hair. I will give you 3 fairly easy options to try and replicate her beach hair at home. This style tends to work with longer hair (past shoulders) and in my experience works with straight to medium wavy hair. Different density requires different techniques, so give these a try and let me know how it works out for you.
Option 1: With freshly washed and conditioned hair wring out excess water and distribute either a lightweight styling mousse or volumizer. Section your hair horizontally and start at the lowest section (base of your head neck area) and twirl the section around your fingers. Next take another horizontal section and repeat. Do this until you reach the top and all hair is now twirled! Use different size sections to get varied results. Once you've twirled all your hair begin slowly drying with a diffuser. The aim is to gently dry the hair, the slower the better. This is not a technique to be used when you are trying to rush out in the morning to catch the subway in -30 Toronto weather.
Option 2: Using cotton rags is another novel way to achieve this look. Where can you get the rags? Well you know those old ratty t-shirts that your significant other insists on wearing regardless of how many holes they have? Yup, you got it. Cut the shirt into long pieces, with each piece being 1-2 inches wide. With damp hair (this style seems to work on 2 or 3 day old hair depending on oiliness) wrap the ends around the center of the rag and then wrap the rag upwards until it reaches your head. Once you reach your head, you tie it in a pretty, but GENTLE, knot and leave it in. You can let it air dry, or apply some heat (preferred). This method requires experimenting with different size sections and wrapping techniques. Anyone who has had the unfortunate experience of having a perm, or seeing a perm wrapped will understand this method best. Think of the cotton rags as perm rods, and your hair as loose Gisele like beach hair!
Option 3: The beach. Yes, what nature does best is hard to achieve naturally, as witnessed by any woman who has ever been to the beach, got her hair wet with salt water, and then lied in the sun to dry off. When I was in Sicily last summer, my partner Stephanie had such beautiful beach waves she could have given Gisele a run for her money. Sicily has that effect on people.