Hi Elizabeth,
Our world might be full of colour but for some reason we still like to see is in black-and-white. Part of the reason for this is that black-and-white photography really is the distillation of good image making; without the distraction of colour you really do have to start analysing light, design and emotion.
I do like this photograph, and I am curious as to how the dog does seem to have two shadows (two suns?). There is not a lot that I would do to change this photo, but the next time you are in this situation I would be inclined to get a little lower (by kneeling on the sand) so that you are reducing the space between the dog and the horizon.
For some reason most photographers see the world from eyelevel or about 1.5 metres from the ground; this might be and most of us to the world every day, but it does become rather predictable. By getting lower we change the perspective of the scene and suddenly it looks a little bit more interesting.
Cheers, Anthony.