If the person in the foreground had more to the left you could of had everthing more central in a triangle shape making this even better. I like the way that everthing is on three layers.
My only suggestion is probably impossible, but . . . If the liner could have been just a bit more to the right, it would have felt more balanced. the swimmer almost balances it, but he is a lot smaller than the ship. I really like the way you have gotten three different "uses" of the ocean captured.
This photo has a lot going on. You captured three worlds in one, all three of which are most likely completely unaware of the others. I love the feeling of this photo.
Nice use of ROT and placement of objects, however, all three are competing for my attention, and I'm not sure which to focus on. I know you wanted to show life at the beach, but picking one subject would've worked better in my mind. I like how the boy is about to dive into the water.