Someone, somewhere thought this would be a good idea. You can almost picture the pitch, probably born in committee:
I know! I know! Let’s put a giant shark… I mean a GIANT shark in a movie with, with, with a giant octopus! The biggest octopus you’ve ever seen, no, even bigger than that! And then they fight each other! It’ll be great, and we’ll get some big name stars, too!
And it will go straight to the home video market.