Explore our collection of fish (more designs coming soon)! Fish are characterized by having vertebrates, living underwater, breathing with gills, having fins, and laying eggs. But there are always exceptions! Did you know that some sharks - like the great white - give birth to live young, called "pups"? Others, like the lungfish, have both gills and lungs, and can live out of water for several years, buried. And some catfish can walk! Jellyfish and starfish are not fish, but seahorses are.