Europa is one of the moons of Jupiter. It is an ocean planet but, due to its distance from the sun, its surface has frozen. The planet interior is kept a liquid by the gravitationally indueced 'Tidal Flexing' caused by Jupiter, Ganymede and Callisto. At the soldid sea bed, this has caused volcanic activity which means all the bmarine life forms are held in an habitable belt of warm water, between ice and Magma.
The Multi-cellular creatures near the surface have a food chain with microbes at the bottom. The microbes get their energy from the sunlight which streams through, but also a process caused by radiation hitting the ice which creates chemical energy. Some animal life here has evolved vision and are well adapted to the cold water enviorement.
Creatures further down get there energy from the volcanic vents via Chemotrophy. They don't have eyes since no light reaches down below. The creatures here have had to adapt to the greater water pressure and have done so in a variety of ways.
Throughout its history, many indegionous populations have devoloped of sentient creatures, however these have never devolped any further before they have died out.