When I saw this illustration I knew this is the look I wanted for this page with the ghost explorer, in human form, falling into the sea. The difficulty with this image was to show he's just fallen into the sea with the use of bubbles.
Looking at reference images of people diving into water helped to work out where the bubbles would look like and what area of the body would cause the most amount of friction therefore the most amount of bubbles.
But the white I put behind the bubbles was too solid so I then was shown how to soften it to make it look more natural, which worked a lot more.
Also another way I thought of showing that he's just fallen into the sea was to drawn horizontal lines slowly getting closer together as you go down the page going into black.