Macropinna microstoma, or the barreleye fish, is a deep-sea species with a transparent head, allowing its barrel-shaped eyes to rotate inside. Living at depths of 600–800 meters (1,968–2,625 feet), it detects bioluminescent prey in near-total darkness. Scientists only studied dead specimens until 2004, when MBARI captured the first live footage, revealing its unique movement and hunting behavior in the deep sea.