Why are eyes of simple marine animals special?

The simplest forms of eyes are not eyes in the sense we know but light- sensitive areas called eye spots which can only detect differences between light and dark.

Eye spots are found in certain algae and single- celled marine organisms. over the ages, some simple forms of marine life devoloped primitive eyes called ocellim which can distinguish between light and shadow, though they are unable to form an image.

The microscopic marine organism called Copilia has remarkable eyes which make up more than half of its transperent body, and these eyes can actually form images.