With nearly 95% of our oceans still unexplored, it's hard to imagine what's lurking deep under water. But thanx to deep-sea cameras, advanced technology and amazing enthusiasm, we know that there're pretty incredible creatures that live deep in the ocean. In this video I'm gonna show you the largest sea inhabitants! One of them is a jellyfish that can compete with the blue whale's epic proportions! You'll also meet a huge prehistoric reptile that lived in the waters all over the world!