Houndsharks are a diverse family of around 45 species, including the Leopard Shark and Common Smoothhound. These sharks are found in warm and temperate waters and have unique features, like large dorsal fins and nictitating eyelids for eye protection. They are important for divers to know, as the Leopard Shark is common along the Pacific coast, while the Common Smoothhound is endangered due to fishing pressures.