Size: The spined pygmy shark, a deep-sea shark, is one of the smallest at only about 7-8 inches, while the whale shark is the largest shark, and fish, at about 50 feet in length. Although lifespan varies by shark species, most sharks are long-lived and generally tend to live for 20-30 years. Species like the spiny dogfish and the whale shark are believed to live for over 100 years!