Gradient’s parameters:

 



It’s time to picture a cloud of white color under the ship, using for this operation the Pen Tool (P) and correcting its size with the Convert Point Tool.



Make a click on the same layer on Add a Mask option on the layers’ panel and choose a standard brush, Brush Tool (B), of black color to clean out the cloud’s part indicated below.



Find in Internet a picture representing a fish.



Cut it out and insert it on our picture.



Make three copies of this layer and choose again the Free Transform option to place the copies as it done next image.

 



Create a new layer and choose again the Brush Tool (B) and the color #D3D3D3 to picture above each fish several air bubbles.



Find in internet a picture with a tree, cut it out and introduce it on the basic picture.

 

The picture is finished!

View full size here.