The monster looked like...
...an anthropomorphic anteater with fins and teeth.
"Just repeat to yourself, 'It's just a show; I should really just relax.'"
Oh no, another anteaterphobic from the Raul Julia club. Would you stop with the anteater bashing? Some of my best friends are anteaters, you know.
shareIt looks to me like the creature's head had to be designed to fit around the diver's mask/helmet.
There is a version of the movie in which we can hear the scientist's thoughts, after he turns into the monster; when he looked at himself in the mirror, he said something like "What?! It doesn't look anything LIKE a catfish!"
- HOW kin I be so brainless, when I is so smart?