this picture was made using 3 photos: shark, crashed plane and rocky road witch was used for ocean bottom. tools used: gradient tool, brush, glass filter, masks
I used gradient tool and glass filter to make  water surface then i cuted out shark by using eraser tool after that i puted all 3 images in one window then using mask tool i merged them together and and using hue/saturation tryed to make image a little bit darker.
Original photos: