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The original looked like a huge hulking creature frothing the water in a life or death battle against a destroyer.
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In the actual film, the oceans are calm. The boat is smaller and the beast is smaller. You can't tell here, but they also added a bunch of spikes and scales which isn't native to the shark or octopus. Personally, I like the concept art better, but with a name like "Sharktopus" it has to be good.
Matt is really good at creating bizarre imagery so make sure you check out his other work at http://www.mcleach.com/illustration.html
What do you think of Sharktopus? Will you be watching it?