Painting an underwater scene on your wall isn't as difficult as you might think. This method is perfect for beginners because it uses two simple techniques that fool the eye, creating the illusion that you're standing at the bottom of the ocean looking up toward the surface. One technique is simply painting a bullseye-like pattern on the wall to form a faux underwater look. The second technique uses size to indicate whether an object is closer or farther away. It's fairly easy and can be applied to many different marine creatures. This allows you to customise your underwater mural by choosing the main subject of the wall painting.
First, tape off the ceiling, baseboards and other walls with painter's tape. Cover the floor with a drop cloth. Using your paint roller and tray, paint the wall with primer and give it a few hours to dry.
Measure the top of the wall you're using for your underwater scene and find the centre. Use a pencil to lightly sketch out the semi-circle locations on the wall, using these guidelines: Put four semi-circles of colour from the middle top to the bottom of the wall (click link below to view an example). The first, white semi-circle should cover the middle third of the wall at the top and should not extend down very far. Make each semi-circle larger than the one before it, and closer to the sides of the wall than the one before it. The final dark blue circle should take up the bottom third of the wall and go all the way to the sides and bottom of the wall.
The semi-circles will be painted white, light blue, blue and dark blue. Using your mini roller and tray, paint the white semi-circle at the top of the wall in the middle first. Immediately follow with another semi-circle, this one larger, of light blue. You want to paint the first part of the light blue semi-circle right after you finish the white one so that you can blend the edges of the paint together. To do this, brush the edge where the two colours meet with a dry paint brush while both colours are still wet. Repeat with the rest of the colours, following your pencil outline. Allow the paint to dry completely.
Now it's time to paint your wall with underwater creatures -- any that you chose -- using your artist's brushes. If you're not an artist, it's OK to use stencils. So let's say you're painting dolphins and you have three stencils: small, medium and large. Use the small stencil to paint dolphins in the white area and the top of the light blue area. Then use the medium stencil to paint dolphins in the light blue/blue area and the large stencil to paint dolphins right in the centre of the bottom of the dark blue area. The small dolphins will look far away and the large dolphins will look close, so your completed underwater wall mural creates the illusion that you're at the bottom of the ocean looking up.
You can use any marine paint shades, from dark blue to aquamarine, for your background. Just make sure one of the shades is white and the other three are from the same colour family (i.e. from the same paint colour sample strip at your local home improvement store).