Let me start off by saying that this movie is without a doubt, bad. It's so bad that I couldn't watch it all in one sitting as it was too painful. I watched the first half one night, and the other half two nights later. This movie sucks super hard. The acting is offensive, and the terrible writing and characters don't help. The special effects are ugly to say the least, and it was clear that they didn't have much of a budget based on the quality of the animations and how frequently they reuse the same ones over and over again. The story is completely non-sensical, and riddled with plot holes and logical gaps. As far as I can tell, there isn't even really a climax. This movie tries to be campy, but it even fails at that. There are the occasional laughs peppered throughout this shoddy attempt at filmmaking, but overall it's just bad. Now let's get into the nitty-gritty of just how bad it is.
The film opens with two marine-biologists in a really shitty submarine set looking for whales off the coast of Alaska while some army guy is in a helicopter above them apparently about to launch some top secret military experiment. The attractive, single, female marine-biologist keeps commenting on how strange it is that there are so many whales in one place. The chopper pilot then drops some gadget into the ocean which emits waves of some sort that somehow releases the titular duo who have been frozen in ice for millions of years (because that's how cryogenics works, right?). The helicopter then explodes for no apparent reason, while Mega Shark and Giant Octopus completely ignore the submarine and each other despite the fact that when they awoke they were locked in a life or death struggle. This all somehow explains the strange behaviour of the whales who I guess had some sixth sense telling them that a piece of human technology was going to release the deadliest sea creatures to ever exist, and this same instinct told them to swim en masse towards this certain doom. This the first of many times that the movie won't make any sense.
The next time happens five minutes later when the scientists arrive in San Francisco. It turns out that took the sub for a joyride from the Californian marine institute that they work at, took it all the way up to Alaska, and then came back without getting caught or reprimanded. By the time they get back, it seems that Mega Shark and Giant Octopus have begun their reign of terror as a whale carcass has washed up on shore. For some reason this event is of intense interest to the government who have agents all over the place despite the fact that everybody dismisses the incident of being of no significance. All of them wear sunglasses. In fact, virtually anybody who works for the military or the government and doesn't have a speaking role, wears sunglasses at all times no matter what. The attractive, single, female scientist sneaks a peek at the whale at night when no guards are around (I suppose they figured the police tape would be enough of a deterrent) and finds a large tooth embedded in the whale's body. She takes the tooth to her Irish friend/mentor and he tells her that it's the tooth of Megalodont, a giant prehistoric shark.
Meanwhile we get our first real look at the incredible CGI in this movie when Mega Shark straight up jumps thousands of feet into the air and catches a passenger jet mid-flight. I think this may very well be the most ridiculous scene ever put to film. It's unbelievably retarded and is made even more stupid by the terrible acting that accompanies it. A guy is sitting on the plane when they hit some turbulence. He gets nervous and an attendant comes by to comfort him. For no reason at all, he tells her that he's getting married tomorrow. She has no idea what to say to that so she just walks away. Then he looks out the window and sees a giant, poorly animated shark jumping out of the water. He shouts, "holy shit!" and then we are treated to a cheesy explosion. At the same time, Giant Octopus tears apart a Japanese oil rig in what can only be called an orgasm of complete nonsense. I can't even begin to describe what happens, because when I think about it I realize that I still don't know what the fuck was going on. There is one lone survivor who I think is supposed to be Japanese, but he might also be Australian. I actually have no idea who he's supposed to be, but that doesn't matter because he only exists to introduce the final main character, a Japanese marine-biologist who is doomed to become the love interest for the attractive, single, female marine-biologist. He asks the man some irrelevant questions, who is being secretly held since apparently nobody is allowed to know about the whole shark/octopus thing even though by this point there have been tons of reported attacks seen by tons of witness. The Japanese man then departs for San Francisco to meet up with Irish mentor and attractive, single, female scientist.
About this time, a video arrives at the home of Irish mentor where they are all staying that was taken from the submarine, and apparently has footage of the awakening of the sea monsters, but all you can see is a black mass, though the characters adamantly claim that you can clearly see them. Then some military guys arrive and arrest them at gunpoint since obviously there is no way they would have come peacefully to work on solving the problem with access to government resources. Now we get to see a string of montages of the scientists mixing Kool-Aid together and shaking their heads in disappointment (cuz that's how science works, right?).
Meanwhile the navy is trying to take out Mega Shark, but little do they know that high-powered guns have no effect on sharks. All you see of the shark is his fin sticking out of the water as it slims closer to the battleship. Except for it never gets closer because they just replay the same shot over and over again, like that scene in Monty Python and the Holy Grail when Sir Lancelot is storming Swamp Castle. The interior of the battleship is just a room that's always bathed in red, has a bunch of random machines and buttons all over the place, and has a steering wheel. They fire their guns a bunch and then somebody reports that Mega Shark is down, because he disappeared from their radar. But then he comes back unexpectedly since radar wasn't designed to keep track of massive sharks twice as large as an airplane. The captain stands there looking like an idiot, doing nothing, and then explosion. It should be noted that this scene is reused later, and is exactly the same in every way except for there's a different captain.
The Japanese scientist and the attractive, single, female scientist decide to have sex since they figured that they must be in love or something, I don't know. After doing the deed in a closet in a military installation without anybody noticing, they realize that pheromones are they key to defeating them. One chemistry montage later, and they have the pheromone that is apparently nuclear waste as it glows green. The plan is to lure the sea beasts into highly populated areas where they can... I don't really know where they planned on going from their. Needless to say, it ends with the Golden Gate Bridge being bitten in half.
Plan B is to use the pheromones to lure Mega Shark and Giant Octopus to each other so they can duke it out and kill each other since obviously it's been bred into their genes to have an irrational hatred for one another. At no point does anybody ask, "Hey, what happens if instead of both of them losing, one of them wins?" So they set out in a dangerous mission in some submarines to bring the two together in the middle of the ocean. A bunch of subs are destroyed and many die in the process, but it's all worth it to see the movie live up to the promise of its title. I'm just kidding, it's the most anti-climactic monster battle in the history of cinema. This movie is one and a half hours long, and Mega Shark doesn't actually fight Giant Octopus until the final fifteen minutes of the film, and when they do all you see is Giant Octopus wrap its tentacles around Mega Shark who squirms for while, escapes, bites one of the tentacles, gets caught again, rinse and repeat. Finally they sink to the bottom of the ocean, locked in death's grasp, and Japanese scientist, and attractive, single, female scientist have a make-out session. The end.
If you still want to see this movie after reading that, then do everything in your power to avoid paying for it. I watched it during my free month of Netflix on the PS3, and even then I still regret it.
Bonus points to whoever can tell me what the filmmakers were thinking when they made this shit that isn't fit to be called a movie.