I think it's a wonderful idea and a wonderful quilt! I see what you mean about the sea monsters in dunce caps. I think what I would do is remove just that one row, add a row to the bottom of the sails with piecing that looks like sailboat bottoms, add a strip of white underneath the sailboat bottoms to separate them from the waves, and piece that row back in. It would make the sails look like a part of sailboats, and the sailboats would "float" on the white separating strip. If you don't add a white separating strip, see if you can shift the row of sails to the right or left so they are not sitting directly on the waves.
I just think this is a wonderful, fun quilt that will delight somebody for ages!