Good job dealing with the midday sun.
I will only comment on the last 2 images in that they are great examples of the 2 different styles of Bikini Photography.
Typically bikini photos are intended for publication and or use in catalogs and such they are created with with a specific audience in mind. In most case the predominant audience will be either male (mens magazines Maxim, SI, American Curves, posters etc.) or female (catalogs, womens and fitness magazines etc)
While the male audience will indeed like both poses the more open legged, crotch to the front is a typical pose in the male world albeit in most mens mags she would have had he knees a bit wider. This shall we call it full frontal pose is rarely seen when the key audience is female.
The female audience is far more likely to see poses that are more angular (feminine) with hips and shoulders rotated closing off the crotch and presenting a bit more silhouette.
So one should always keep in mind the intended audience when working with bikini models. If you happen to be shooting for a product catalog and return to a client with a bunch of full frontal shots the client is likely to be disappointed in the shoot even if it is technically perfect simply because it won't be as effective in reaching the target demographic.