Cheryl, this picture is awesome! I was out of town for this whole challenge and just got back to check in. I'm shocked that it didn't place way, way at the top.
Lotta pictures like this where the brightness of the blurred background detracts from the subjuct. While the texture and shadows makes this more interesting the bright background is still problematic...
I think this picture would have more impact if you could have had a person with a surfboard in the background, barely in focus. Otherwise, I like the waves in the background.
The horizon seems tilted, and where's the surfer in the background that's mentioned in the title? The division between sand and sea could also be further from the centre to improve composition. Think rule of thirds. I'd also like to see the sandals maybe facing towards the sea and help draw the viewers eyes out there.
I am glad you gave a reason that the shoes are empty. If the owner had gone surfing, i would have roated the camera around to portrait so that more surf - preferably some waves, most desirably a surfer were visible in the background.