Great job! This is very pretty, although not extremely interesting. Nice use of light and color and perspective though. Good job keeping with the theme of the challenge. Raising my original score from a 4 to a 5, definately is not below average.
Can I nitpick here just a little? You have such a good composition going except for that disturbed sand around the kelp/seaweed object. Those footprints take this just out of the "great" category... But one heck of a good idea, for sure.