The Ultimate Predator
Megalodon was a prehistoric mega shark that no living creature ever wanted to see. With a bite force of about 20 tons, and teeth as big as an adult's hand, when Megalodon was hungry, I'm sure finding lunch wasn't very hard. Megalodon averaged about 40 feet in length, bigger than the biggest known T-Rex skeleton. Sometimes, Megalodon even snacked on whales!! Megalodon was thought to go extinct a couple million years ago, but there are still the people that claim to have seen it. For example, on a fishing wharf, (this particular one happened to be about 115 ft. long) and two of the fishermen had been keeping all of their catches in cages down beneath the dock. Thats when a pale gray shark, "As big as the wharf!" the fishermen described, swam in and ate all of the cages, and everything within them-whole!
There is some more evidence suggesting that this monster still exists. For example, in 2009, when a sonar scanner found a deep sea trench just off the coast of Monterey (I think), and scientists said it was possible for extreme amounts of life to be living within it. And then again, there are always the people that say they've seen it swimming around......

Wikipedia. Megalodon. N.p.: Wikipedia, 2011. Web. 27 Sept. 2011.

Some Megalodon teeth got to the size of a full grown man's hand!!

The people on the boat are thinking, "Awww, look. It's a little fishy!"

This is a computer generated image comparing the size of the beast to the woman swimming next to it.