Megalodon - is an extinct species of shark that lived approximately 15.9 to 2.6 million years ago, during the Cenozoic Era (middle Miocene to end of Pliocene). and is regarded as one of the largest and most powerful predators in vertebrate history.
Scientists suggest that Megalodon looked like a stockier version of the great white shark.
The most common megalodon fossils are its teeth. Diagnostic characteristics include: triangular shape,robust structure, large size,fine serrations,and visible v-shaped neck. Megalodon teeth can measure over 180 millimetres (7.1 in) in slant height or diagonal length, and are the largest in size of any known shark species.
But some people believe that the Megalodon is still roaming in the ocean right now. Remember 95% of world's ocean is still unexplored. But I doubt it still exist