Saturnyn

The Saturnynians were an exo-skeletal, insectoidal species of fish from the planet Saturnyne. They were notable for their many limbs and their two curved canines. They constantly needed to either consume or come in contact with water and this included moisture in blood. If ever they used perception filters, their teeth would remain and they would smell vaguely of fish. (DW: The Vampires of Venice)

They also resemble deep dwelling sea life in the respect that they have a great sensitivity to light and while they are able to travel in daylight, exposure to direct sunlight will cause them to explode.

The species used perception filter technology, which they used to blend in with the human population of Venice. However, this camouflage was not perfect and gave rise to vampire-like qualities among those in the school. Since the technology couldn't hide reflections, and the human brain couldn't process the two conflicting pieces of information, anyone who saw a member of the species near a reflective surface saw a human without a reflection. Their fangs would also be seen when they fed due to the human subconscious perceiving danger and attempting to alert the conscious mind.

Some time in the species' history their home-world was besieged by the cracks in the universe, ranging from small cracks to cracks that consume the planet's sky. At first the cracks appeared to pose no real danger and the aliens were able to observe other worlds through some, and "silence" and the "end of all things" in others. Eventually, however, the true nature of the cracks became apparent and Saturnyne was lost. The species itself was not lost. Deciding to take their chances with the cracks that showed other worlds, the Saturnynians fled to worlds with oceans like their own planet. A colony arrived in Venice though it is unknown if any other members of the race made it to other worlds.