Putting the laws of time and plausiblity aside, picture a battle between the megalodon (a prehistoric shark with a six-foot jaw span) and a giant squid (reported to be the size of a school bus). Who would win?
The shark for sure! Squids are soft creatures and though the giant squid is a strong creature the sheer size and power of a megalodon would rip that squid to shreds.
Also, I <3 megalodons. I have a book by Trent Alton called "Meg", it's awesome and "Beast" by Peter Benchley.