In this tutorial you will create an interesting Underwater desktop wallpaper.
Open a new file that would have
1600x1200 px and
72 dpi. Make use of the next instrument

to create the background for the picture to be next.
Blending Options-Gradient Overlay
Gradient’s parameters:

Apply the same instrument to represent the rays, penetrating the water. Make use also of this tool

on the layers to clear out a little the figure with a transparent brush, the way it is demonstrated below.
Fill 0% on the layers.
Blending Options-Gradient Overlay