Megalodon was a giant shark that lived about 28 to 1.5 million years ago. It's maximum length was about 46 to 60 feet. It's teeth were 7 to 8 inches long.
A Megalodon toothe by two teeth from a Great White
The scary thing here... Megalodon might still be alive! A giant, 100 foot long white shark was seen sometime in the early 1900s. There is enough space in the deep ocean for giant, unknown creatures.
If you say Megalodon is not alive today, consider this. the Coelacanth is a fish that was supposed to have gone extinct with the dionsasurs 65 million years ago. it wwas discovered alive off the coast of Africa in 1938. If it had survied 65 million years after it was supposed to have gone extinct, why couldn't Megalodon survine 1 million?