"We tried to find something that is more or less logical, we know we’re not totally logical. But it’s just something that the audience can accept. What we have here [is that] because of global warming, the glaciers are melting and we have the frozen sperm of a prehistoric shark. As the glacier melts the sperm comes out, wait no it’s a fertilized egg, and the Dinoshark grows from that. Whatever works!"

Roger Corman Justifies Sharktopus’ Awesome Existence With “Logic” - Sharktopus - io9