Europa's surface is marred with huge, curved cracks, called lineae, which may - depending on the thickness of its icy crust - expose the subsurface ocean to sunlight.
Pictures like the one above (Source: http://www.daviddarling.info/encyclopedia/E/Europalife.html) show these cracks in the ice sustaining complex multicellular life forms which photosynthesize the sulight pouring in through the cracks.
Is this reasonable? More specifically; would the cracks remain stable long enough for complex multicellular life, specialized to live in the cracks, to evolve there? They'd potentially have to stay put for hundreds of millions of years, maybe even a billion years, in order for those kind of life forms to arise.