This is stunning; compositional elements aside, it has almost 3D color and depth, without too much graininess.
I like the pose, very impressionist or post impressionist in mood. almost pointillist.
First of all, your composition is too tight. Her fingers are so close to the border that it makes me anxious! You were so close to cutting off part of her hand entirely.
Photographing people requires much better lighting conditions (perhaps sunset when you would get gentler light and a more impressive sky). The sun is so harsh that it caused her face to scrunch up and look grumpy...not attractive. In addition, her shoulders are too high. The neck is an important thing to feature on a woman and in your image, she doesn't have one.
I understand the HDR experimentation...but it was the wrong picture to pick for it. The HDR brought out too many details in her skin and made her look probably 10 years older than she really is. HDR is not the right technique to use for photographing women in bikinis. The only positive of the HDR that I see...is in her hair and on the foreground sand. The technique brought out many beautiful textures.
I don't like the seagull...it's a bit distracting to me.
Your colors need work also. There's a lot of grays in the background. There's no pop in the sky. I also agree with the majority of comments about the halo.
Also, make sure you take a close look at your images and clone out the sensor dust...there's one I see on the upper right of the image.
Nice framing and colors, but the lighting on her face gives her a bit of a scowl and some odd shadow lines that are unflattering. The post processing is good for the most part but the masking around her head is a bit sloppy, leaving a halo of brightness, showing the darkening of the background. I know those dodge lines don't bother some, but for me I wonder if it would not have been better to either cut the dodge in all the way, or feather it out so the fall off was more gradual. As is i find it one of the most dominant elements int he image.
I know I'm not the first or the last to say it, this is really (really) overprocessed.
The tonality (tonemapping) and the halo around the girl is not appealing.