The barreleye (Macropinna microstoma) has extremely light-sensitive eyes that can rotate within a transparent, fluid-filled shield on its head.
The barreleye fish’s actual eyes are awesome. Unlike those of most fish, the eyes of the barreleye fish point in the same direction, which gives them excellent binocular vision (where the two eyes form a single image). Encased within a transparent, fluid-filled shield covering the top of its head (which may help it to see better in the dark), its eyes can either point upward, searching for prey in the dim light above them, or forward, when swimming toward that prey.
In addition to their amazing “headgear,” barreleyes have a variety of other interesting adaptations to deep-sea life. Their large, flat fins allow them to remain nearly motionless in the water, and to maneuver very precisely. Their small mouths suggest that they can be very precise and selective in capturing small prey. On the other hand, their digestive systems are very large, which suggests that they can eat a variety of small drifting animals as well as jellies. In fact, the stomachs of the two net-caught fish contained fragments of jellies.
Quit a cool fish no?