Thanks for the tip Paul, I will definately keep it in mind. I do recall that I took very good care to be at eye-level with the children, and then this happens. What is most important then? The eye-level, or the horizon? or is there a good way to combine both?
This is a nice looking kid, with a very cheeky grin! Try to keep the horizon level, and get down to the kid's level so that we can see into his eyes. Also try to keep the shore line or horizon cutting through his head. These little points will make it a much more "artistic" photograph, as well as a memory of a happy day at the beach.