Michael and Rachel are devastated when their six-year-old son dies in a tragic accident. When a stranger offers to bring the boy back to life, they take the offer. However, the child who returns is not the child they once knew.

When another Mega Shark returns from the depths of the sea, world militaries go on high alert. Ocean traffic grinds to a standstill as everyone lives in fear of the insatiable beast. Out of options, the US government unleashes the top secret Mecha Shark project -- a mechanical shark built to have the same exact characteristics as Mega. A pair of scientists pilot the mechanical creature as they fight Mega in a pitched battle to save the planet. But when faulty mechanics cause the Mecha to go after humans, the scientists must somehow guide Mega to Mecha in hopes that the two titans will kill each other - or risk untold worldwide destruction.