Scientists just discovered the "Demon Cavefish" (Demogorgonichthys arcanus), an eyeless, see-through species living in dark caves beneath an Alabama facility. Meanwhile, the deep-sea Oneirophanta sea cucumber thrives in the high-pressure darkness of the Indian Ocean seafloor. Which of these extreme adaptations is more fascinating? Sources: Mongabay, August 26, 2026; UAH News. Original editorial visuals.