This one is pretty self explanatory. Everyone takes a walk along the beach and this one was a great shot cause I was able to get the footprints in the sand.
This is a great picture with a nice depth to it and an interesting perspective. Have you tried using the clone tool in photoshop? I think you photograph would benefit from this tool - you could remove the people from the water to centralize the focus on your friend.
This is a nice view of a typical beach day :) I like the line of footprints--they add a nice "story" element and lead my eyes to the subject of the picture, your friend. I do agree with Heidi in that it would be nice to focus in on your friend a bit more.