In this image, professional surfer Kelia "Sister" Moniz displays a classic flirtatious body language cluster. Here she looks backwards over a raised bare shoulder with her head tilted slightly down and a sincere smile. She is walking and this may or may not be a posed shot.
To increase the "flirting" power of this nonverbal cluster her head should be tilted downward a more - this acts to opens the eyelids to a greater degree and therefore gives them a "larger" appearance. Larger eyes are a universal quality of beauty - and this configuration also engenders a protective instinct in most men and thus also attract them like bears to honey. A sincere smile has partially closed eyelids (mildly so here) while a social smile's eyes are opened more widely - so ironically to some, a good quality social smile with these larger eyes - in the context of this nonverbal cluster - are quite magnetic to males.
Additionally a very slowly and subtly projecting tongue for a slightly prolonged time (e.g. three to five seconds provided the man is looking) or a gently bitten lateral portion of her lower lip - would also "dial up" the provocative power of this nonverbal cluster.
Although Ms. Moniz displays this cluster only partially, it is powerfully attractive and all but the most clueless males will be drawn-in once this body language look is flashed.
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