Marvel Comics #1 was published by Martin Goodman’s Timely Publications, which became Atlas Comics in the 1950s and Marvel Comics starting in 1961. According to Nostomania, it is the 6th most valuable comic book in existence.
One of the first comic book anti-heroes, the Sub-Mariner also bears a passing resemblance to Nietzsche’s Übermensch, literally “overman,” but often translated as “superman.” (Interestingly, the character of Superman created by Jerry Siegel and Joe Shuster was based on a confused interpretation of the Übermensch, and first appeared as a villain bent on world conquest in a story called The Reign of Superman ). Here Sub-Mariner’s creator Bill Everett refers to him as an “Ultra-man of the deep,” an “avenging son” who will soon wreak catastrophe upon the “white Earth men.”
The only image I could find from “The Atlantis Mystery” of Action Comics #18 is below. The story’s hero is Zatara, a magician (invisibility, mind control, telekinesis, matter manipulation, etc.) who casts spells using backwards speech. The creative team is Gardner Fox (writer) and Fred Guardineer (pencils and inks).
And here are some pages from Action Comics #17, featuring an Atlantis reference along with a panel showing “the temple of ancient Atlantis.”
These are the first two appearances of Atlantis and the Atlanteans in the Marvel and DC universes: it’s immediate at Marvel, and sixteen issues short of immediate at DC.