How do they measure the length of the shark? Do they include the tail as well? If so, then a 3m great white is about half the size of what it could reach.
Based on the image below (which is a 6m great white), a 3m would be half the size, and fit completely inside the Megalodon's jaws.
Wouldn't that 3m shark be dinner for say an 8-10m great white?