Films: Octoman (1971)
Height/Weight: That of an average human.
Summary: In the grand scheme of things, "gill-men" are rather limited in their scope. You have tons of sea creatures to choose from, and you keep going the safe route with what that Black Lagoon resident started. But now we can shake things up a little. With cephalopods!
History: Somewhere in Mexico, the radiations levels in a lake are quite frankly horrible. Some much so that some inexplicable freshwater octopi have become mutated into rather grotesque abominations. Chief among them is their vanguard, a bizarre man-octopus who really doesn't like uninvited guests.
Notable Kills: Nothing special
Final Fate: One failed attempt to catch Octoman later, the token girl decides to offer herself in exchange for her friends' safety. Alas, the men just shoot Octoman at close range anyway, causing it to stumble into the lake and die.
Powers/Abilities: Apparently intelligent enough to understand human speech.
Weakness: Cannot stand dry environments, and must keep skin moist.
Scariness Factor: 2.5-It's as easy as not going near that contaminated lake. And even if you somehow get near there, you can laugh at how this thing flails its arms around like a dingus.
Trivia: -Almost right after shooting this film, chief cinematographer Pier Angeli died of a drug overdose. Ouch.
-Octopi cannot live in fresh water. In fact, most cephalopods have evolved to exist nowhere near those places. The one exception is a species of squid found in Chesapeake Bay.