Over all, I like this picture I'm not very good in technique, though to my eye doesn't see mistakes.

With this title "Lost" and a lonely child in a blue desert of water that seems to be the end of the world... Poor thing I feel like going to see him/her, ask where is his/her mom, why is s/he alone there, where s/he comes from... Did s/he ran away? What happened? D:
I personally think that the lighting, the color, the pose, with the title, does all the impact here.

Blue like the infinite ocean and sky, but also cold and sad.

And then comes the darkness. The silhouette is dark itself; it could mean, s/he feel in the dark, abandoned, or s/he feels empty, or sad...). The surounding is dark too, giving a slight feeling of suffocation or "too tight", but also "blindness" (like "I can't see where I came from and where I should be going now").

The fact that the child is looking at his/her feet, the way those feet are placed, I think it adds to the impact of loneliness and sadness. Though, without the effect of light, blue and darkness, this kid is probably simply having fun watching the waves and tides over his/her toes, this is a good example of how the emotion through a picture can be changed only by some very light effects mentioned above (light/dark, color, pose & title), whatever if it was a spontaneous or planned shot.

This is my two cents
This is what I see with this picture.