Barreleyes are an odd family of fish. Their name comes from their protruding eyes. What makes the eyes odd is the fact that they’re housed inside a transparent soft-tissue. Beyond it is where its skull starts. This is because they can apparently swivel their eyes up and down as well as side to side. This allows them to see prey both up and ahead. They live deep enough as to be difficult to find (some 400-2500 meters) but not in the extreme depths.
Barreleyes are extremely lonely fish too. They spend their lives completely alone not even getting together to reproduce. The eggs and sperm are released to roam free until they meet each other after which they incubate and are born, alone. They’re pretty rare too; the number of barreleyes found with the soft-tissue dome intact is somewhere in single digits. As far as I could find there’s only one set of pictures ever taken of these creatures.