I need to replace the vessel seen in the below image with another vessel. I have already cropped the vessel that needs to be placed there however I am unsure how to create the gradient background seen in the below picture with the bar in the middle. I see that there's a gradient and some lighter 'spots' but I am at a loss how to create this effect in Adobe Photoshop.
If I were to tackle this in Photoshop, I'd first use the gradient tool (keyboard shortcut: 'G'). Both ends would be black and the center would be the lighter blue.
Next I'd use the brush tool with a feather brush (keyboard shortcut: 'B'), and paint the sides. For the center lighter blue I'd use a feather brush with the light color. Alternatively you could create an ellipse (Keyboard shortcut: 'U' or Shift +'U' to cycle to the ellipse shape) and put one in position. Then go to Filter > Blue > Gaussian blur and adjust the radius until you're happy with the look.
As for the rectangle running through the middle, draw a rectangle (Keyboard shortcut 'U') the length you want it to go. Use a black fill, and then drop the opacity. To make it fade like it does when near the boat use the gradient tool again (Keyboard shortcut: 'G') and change the Gradient fill to go from black to transparent.
I would build the background with four basic layers:
1) A gradient for the "sky"
2) A gradient for the "sea" (basically inverse of the sky)
3) A line for the "horizon" (draw a line and experiment with gaussian blur to soften it a bit"
4) A highlight behind the ship; draw a rough outline with the lasso, feather it a bit, fill with white, adjust transparency, maybe blur a bit