The Giant Octopus is an ancient very large form of Octopus capable of attacking seacraft and maiming crews. At some point, the Giant Octopus was frozen inside of a glacier alongside the Mega Shark but was broken out when a bunch of whales rammed against it. The two creatures went on a rampage all the while fighting each other all the while the US military tried to stop them. During one of these fights, the two killed each other.
The Giant Octopus uses it's tentacles to bring in it's prey to feast upon. The Octo could have lived during the times of the dinosaurs, and forward into time. Ancient sailors would tell tales of giant monsters, and most of these monsters were told to be very large squids, that would destroy ships, or drag away crewmen for them to never to be seen again. Giant Octopuses are the stuff of myth and legend and are possibly the inspiration for the Kraken.
Battle vs. Crocosaurus (by KevlarNinja)
On a island of the cost of Florida, the Crocosaurus is guarding her eggs. Suddenly, she notices something splash on the water. It's the arm of a giant octopus! The Crocosaurus swims toward it, seeing it as a threat to her eggs. She swims to the patch of water where she saw the arm. But then, the octopus strikes, wrapping it's arms around her! The Octopus trys to bite her on the neck with it's beak, but her scaly armor stops it.
The Crocosaurus slips out of the octopus's grip. She then turns around and bites an arm, useing a deathroll to help rip it off. The disembodied arm twists and tries to get the Crocosaurus, but ends up sinking to the deep ocean. The Crocosaurus claws at the Octopus, but does little damage. The Octopus wraps it's remaing arms around it's attacker. The Crocosaurus snaps off another arm before getting out of the Octopus's grip. The Crocosaurus swims around and bites the Octopus on the back of the head, and carries the Octopus to shore. The Octopus grows weaker and weaker. The Crocosaurus reaches shore and drags her prey onto shore. Unable to breath, the Octopus dies.
Successful, the Crocosaurus roars. She starts to hear chirping. It's her young. She drags the octopus to the nest as their first meal.
The Crocosaurus emerged victorious due to its sharp teeth and strong jaw which allowed it to rip apart the Giant Octopus. The Giant Octopus also had more tender flesh that was easy prey for the Crocosaurus, as opposed to the latter that had a tough outer scaly body that the Octopus couldn't strangle with mere tentacles.