Differences in the comic.
As everyone knows, comic adaptations are going to differ from the movie in a number of ways and Gorgo, as drawn by Steve Ditko, is no different.
1. Joe, clean-shaven in the film, is given a pencil-thin mustache (and a butt chin).
2. Similarly, McCartin, also clean-shaven in the film, is given a bushy white-blonde beard (and matching hair) which, combined with the fact the comic also makes him overweight, has the unfortunate effect of making him resemble Santa Claus.
3. Sean is (probably unintentionally) drawn much older. He looks about fifteen or sixteen.
4. There's an extended sequence underwater when Joe and Sam first go diving. First, they get attacked by a giant octopus, and then by an orca (I'm not up on UK marine biology, but are orcas common off the coast of Ireland?). Before the orca can devour them, Gorgo appears and kills it.
5. Speaking of killing things, the orca and the usual collateral damage aside (the military and anyone in all those buildings Gorgo's mom destroys), this comic wusses out on the death toll. En route to England, Gorgo does not kill a sailor, nor does he kill one of his handlers at the circus. Also when Gorgo's mom stomps Nara Island flat, everyone (including McCartin) miraculously escapes.
6. For those wondering what Gorgo's name was before Dorkin got involved, it's "Ogra." Also whereas in the film Dorkin changed the name to a shortened form of "Gorgon" for advertising purposes, here, Dorkin just sends Joe and Sam a telegram saying he's changing the thing's name from Ogra to Gorgo with no explanation.