There's an urban legend that the original plan for the movie that would be "Godzilla" actually was for an octopus monster, until the production team became aware of Ray Harryhausen working on "It Came from Beneath the Sea", at which point the monster was changed into a dinosaur-like creature.
While there's probably not a lot of truth to this ("Godzilla" premiered more than six months before "It Came from Beneath the Sea"), it might just be enough of an inspiration for making the monster in this episode an octopus.
Another thing, that shot of the single tentacle coming out of the water reminded me very much of Godzilla's tail doing the same in "Shin Godzilla".
While there's probably not a lot of truth to this ("Godzilla" premiered more than six months before "It Came from Beneath the Sea"), it might just be enough of an inspiration for making the monster in this episode an octopus.
Another thing, that shot of the single tentacle coming out of the water reminded me very much of Godzilla's tail doing the same in "Shin Godzilla".