As someone else said, the closest living relative to the Megalodon is the Great White.
Megalodon is said to have become extinct over 28 million years ago.
Since civilization has developed, and technology has become more sophisticated, you would have thought there would be records of sightings of a huge
dorsal fin, unexplainable bite/teeth marks in water dwelling mammal remains (I think it goes without saying that the Meg would feast upon large marine
mammals like Orcas and whales), you'd probably see a massive decline in large marine populations. I honestly don't think there is enough food to
sustain such a massive predator, and I don't see how such a large predator would go unnoticed.
C. megalodon had enough behavioral flexibility to inhabit wide range of marine environments (i.e. coastal shallow waters, coastal upwelling,
swampy coastal lagoons, sandy littorals, and offshore deep water environments), and exhibited a transient life-style. Adult C.
megalodon were not abundant in shallow water environments, and mostly lurked offshore. C. megalodon may have moved between coastal and oceanic
waters, particularly in different stages in its life cycle.
I know Wikipedia is not the Holy Grail of all knowledge, but they base these theories on the behaviour of it's closest relative.
I realise we don't know everything about what lives in the sea, but you would imagine, that if Meg was still alive, it would be difficult for him to
live in deep waters unless there were A: Many places for it to go, since it is a wanderer, it would have to have many deep places to go, and not be
limited to one area, B: The area it inhabited would have to have a very large amount of food for it to remain in that one area.
We know that there are many deep sea Giant squid, and that would probably be the only food we would suspect Meg would eat. And since we know that the
sea is abundant in squid, we can assume that they are not being hounded by a voracious mega shark.