This is one of "Val's boxes" I used a paint sample card to make this.
This didn't turn out as nicely as the one I saw on Pinterest. I cut the fish and seaweed out from the paint sample cards, and glued them on to a sheet of pre painted paper I did last year, using watercolour and salt to give the mottled effect. There is silver foil on the right side, part of an experiment, so it doesn't really give the effect of the sea!
These two were fun. I downloaded a bunch of stencils on to my hard drive, and printed them out on old sheet music that I found at the opshop. Saw this idea on Pinterest - where else!