Researchers in America have discovered how the unique body shape of a species of cavefish in Thailand gives it a very un-fish-like skill.
The Cryptotora thamicola is blind and lives in caves, in very tough conditions that most fish couldn't survive.
Luckily, this fish has evolved in a way that allows it to walk like a four-legged animal, and even climb waterfalls.
The talent comes in handy because the food which it eats lives on the steep walls of underground caves.
The discovery of this little fish's walking-ability could help researchers to understand how, long ago, sea creatures evolved to be able to live on land.
Footage courtesy of the New Jersey Institute of Technology.