When I first saw this photo, I thought it must be a stuffed toy, not an animal or a fish.
It’s a salamander. Besides its looks, it’s unusual in that it stays in its larval form, like a tadpole that never matures into a frog. It never develops full lungs, retaining its gills and fins, so it lives under water. The axolotl becomes sexually mature in the larval stage.
The axolotl can completely regrow a lost limb.
They are endangered in the wild because of habitat loss, but they are used in labs all over the world because of their ability to regenerate limbs and their embryos which are large and robust.
The only place on earth you can find them in the wild is at Lake Xochimilco in Mexico.