Just a few observations.
The spot where the sand meets the water , Too hard of an edge between the water and the sand. You should see some sand through the water to give depth to the water.
I am guessing from the look of it, you modeled one plank applied the texture then added an array. While this is fine, you should make each plank a separate object. Then apply the texture differently to each object. So you don’t have those darker lines on the right of the dock. This will add variation to the wood planks and also help with depth. Youll have to scale and unwrap every plank, but it’ll be worth it.
Your also going to need to improve the overall lighting of the scene, It is bland and unrealistic for the sky you have chosen. Play around with a sunlamp it’s location and, its size and color. YOu may need a few different lamps at different strengths to accomplish a desired effect. You may want to look into the sun position add on. This allows you to place and synch your light source with the sky. After entering some settings like time of day and hemisphere and time of year. It will generate the proper lighting conditions for you.
The sand quite frankly looks like a hard plaster or concrete floor. Sand is soft, in most cases. I’d consider using a displacement map to give the sand some peaks and valleys.
Also something on the horizon like a mountain range or silloute of a distant coastline, or even the sail of a ship will help give depth to the scene. You don’t need to model it, just find something that will work and apply it with an alpha to a plane. As it looks now, it seems like you could step off the dock and walk a few feet to the horizon. You need to add depth.
I know that it may seem that I just tore your work apart. But on the contrary, I like your idea and concept, I like where your trying to go. But How are you supposed to improve if someone doesn’t point out weaknesses?
Best of Luck