Here is the result should be. Make sure to leave the lighter part (let me say the ground or sand) of the image visible a bit supposed to be a horizon line for the scene as shown by the yellow arrows. If you ever wonder why we should fill the background with radial gradient of color mentioned in step 2, this is the reason why: almost half of the background is now covered by the water texture and the rest which is uncovered supposed to be the part where the light source is coming from. The choice of the color mentioned in step 2 is to match the background with the water texture with hue/saturation adjustment.
Step 5 (Adding more elements)
Now place the dark wood image above the water texture layer in the canvas. Scale its size in such way that its position is right in front of the light source (the half part of the radial gradient)
Mask some parts of the wood to have result similar to the one shown in the screenshot.
Give this wood layer an adjustment layer to alter its color. When the hue/saturation option window shows up, make sure to check Use Previous Layer To Create a Clipping Mask. This will give this hue/saturation layer a clipping mask.
Here is the value of the hue/saturation and the look of the hue/saturation layer in the layer panel. The downward arrow next to the layer is indication of a clipping mask.
Give this wood layer another new adjustment layer with a clipping mask. This time we will give it color balance. Set the value of this color balance layer as shown in the screenshot. This will give the wood image some blue tone.
Finally, go select the wood layer to be active on it and set its opacity to about 30-40%. Select the wood layer including the two adjustment layers with clipping masks above it, and hit Ctrl+G to group them in a new group or folder. I named this new folder BG
Step 6 (More woods)
We should fill the left and right part of the empty space of the scene. We will do this by simply duplicating the BG folder. Duplicate the BG folder and move the duplicate to the right. We can flip the wood horizontally to avoiding uniformity. Arrange its position to the left. We can alter the opacity of the wood layer within this duplicate folder to about 75-85% opacity.
Mask a bit unneeded part:
Duplicate again the BG folder and place the duplicate to the left to fill the empty space in that part. Mask some unneeded part.
Here is the result so far:
Step 7 (Adding a fisherman)
Open the fisherman image in photoshop. Cut out the fisherman as the result shown in the screenshot. We can use any extracting tools which are available in photoshop to do this cut out.
Place the cut out in the main document. Scale its size to fit the composition.
Mask unneeded part of it.
Finally give this fisherman layer a hue/saturation adjustment layer with a clipping mask. Duplicate (Ctrl+J) the hue/saturation layer. Set the main layer to soft light blending at 100% opacity and the duplicate to normal at 100% opacity. Select all the fisherman layers and hit Ctrl+G to group them in a folder. I named this folder fisherman.