If a 60-foot Megalodon were alive today, you could still safely swim in the ocean. To a 50-ton apex predator, a human treading water just registers as floating debris.
To understand why humans would remain relatively safe, it is essential to look at the dietary requirements of an apex predator this massive. Megalodons required an enormous caloric intake to sustain their bodies. Fossil evidence, particularly bite marks on ancient bones, shows they specialized in hunting large, blubber-rich marine mammals like baleen whales. A human swimmer, lacking thick layers of blubber and offering very little nutritional value, would simply not be worth the energy expenditure required for a Megalodon to pursue and consume.
Furthermore, the habitats of adult Megalodons would keep them largely separated from casual swimmers. While paleontology indicates that Megalodons used shallow coastal areas as nurseries for their young, the massive adults spent much of their time in deeper, open-ocean environments tracking whale migrations. Even if a swimmer encountered a juvenile Megalodon—which still measured around 10 to 15 feet in length—these younger sharks primarily fed on fish and smaller sea cows. Much like modern great white sharks, they might exhibit curiosity, but humans are not their natural prey.
The real impact of a living Megalodon would not be on people swimming, but rather on the modern marine ecosystem. The presence of such a massive predator would likely suppress populations of large whales, which currently thrive without a natural apex predator hunting adults. This ecological shift would ripple through the ocean's food web, altering the distribution of marine mammals globally.
Ultimately, while encountering a shark the size of a school bus would be an awe-inspiring and terrifying experience for deep-sea divers or boaters, standard beach activities would remain largely unchanged. People could still safely enjoy the surf, blissfully ignored by the true giants of the deep.