I don't know what it is, but hair like that literally does me in every single time. There is something so sexy about very long hair with big wavy curls in it. Oh, the rest of the model is gorgeous as well, but that hair! Love the yellow highlights on the blue curtain. Adds fun detail that doesn't detract from the shot at all. The pose is a great mix of seductive and innocent. Lighting on the model is perfect too. She looks beautifully tanned without being over done at all. Amazing.
That is a great photo.
Oh yeah! *love* xD