A German man who goes diving underground for a hobby has discovered what scientists say is Europe's first known cave fish.
Spelunker Joachim Kreiselmaier chanced upon the fish in August 2015 while exploring the Danube-Aach cave system in southern Germany.
It resembled stone loaches found in nearby rivers, but with smaller eyes, longer whisker-like barbels, larger nostrils and almost no colour on its body.
In an article published in the journal Current Biology, scientists from the University of Constance who studied the fish concluded that it is a genetically distinct species.
It likely arose within the last 20,000 years and has adapted to life underground.
Cave fish have been discovered in other parts of the world, such as the Pennsylvanian cave sculpins, but never so far north, researchers say.