Whale sharks are the biggest fish in the ocean. And you seriously won’t believe how big they are until you’re in the ocean right next to one! Whale sharks are one of the ocean’s greatest mysteries. They’re almost constantly on the move, and they spend a lot of their time at great depths (nearly 2km deep). So little is known about their life cycles and breeding habits. They can live to be over 100 years – which is no mean feat for an animal so large.