Final outcome

For my final outcome I had to do a underwater scene. Below are some screenshots of my progress.

First, I used the photo of the Greek temple to provide a background, and used the pen tool to remove the sky.I used hue saturation and colour balance layers to change the colour to deep blue. I used free transform to rotate the background. Next I used photos of coral reefs to add in the fore-ground.

After feathering the edges of the coral I added the plane wreck, and more reef in the back to give the picture depth. The feathering removed the hard edges and artefacts from the original source photo. 

For this one I used the gradient tool to add the impression of water and I used the noise distortion to add little dots to give the impression of plankton. I feel the plankton adds realism to the image.

For the final step I added beams of light using the polygon lasso tool, added white and feathered the edges and altered the opacity. I also brought the blue gradient forward a few layers and added fish. I like that the light is shining on the bright parts of the aeroplane.