I selected the girl because, she is looking to the viewer, and is beautiful, the perspective is nice and her body position is attractive. But no all is nice
did you see that the photographer cut a part of her right foot? Thats something to take in account, because youre going to have to fill that part in the future and is not easy. Another thing the resolution is huge! (This is good) and; it has a lot of noise (bad thing), but dont worry, youre almost a photomanipulator and our job is fix, improve and create wonderful images using parts of other images! .The solution is easy in photoshop Filter/Noise/Reduce Noise.
The concept is sunny beach remember? Thats why I selected it, because the sand is illuminated by the sun. I will be weird if is a sunny day and the image that you used was taken in a cloudy/stormy day.
The same of Ground but also, Do you remember where is the light of the sun in the Girls Image? Is in the left well, in this image the sun or light is in the same position.
The Light and Shadowss direction are so important that can be the difference between of a wonderful manip or a piece of shit. The Girls back is illuminated, so imagine if I use a sky stock that doesnt have a source of light?.
Lets talk about the shadow that you are going to put in the image, because you have a sun isnt it? Then you have to put a shadow and determine the direction depending of the direction of the sun, in this case the sun is behind and in the left of the girl, so we are going to put the shadow in front of her and in the right, Is just the opposite position of the lights resource, always remember it . Now look carefully in the Girls Image, in her feet to be exactly, Can you see the shadow? Is a soft shadow why? Because the intensity of the light is also soft.
The secondary subject in the image is almost always small and is far in the distance, can be birds flying in the sky or in this case a little boat in the ocean, but remember the rules of light and shadow apply also here, dont ruin your photomanip with this little mistakes.