"The Comming of... Sub-Mariner!"
The Human Torch sees a bum in a bar who reminds him of the Sub-Mariner so he tosses him in the ocean to see if he can swim. The bum turns out to be the Sub-Mariner and the water returns his memories. Subby falls in love with Sue and uses his horn to summon a monster to eat New York. The F.F. stop it and Subby goes back to the sea.
- Sub-Mariner - First Modern Appearance
- Giganto (Atlantean beast) - First Appearance; Destroyed by explosives!
- The US Army
- Various New Yorkers
- The Human Torch uses his famous "Flame On!" battle cry for the first time in this story.
- Namor swims from New York to the site of Atlantis in the North Atlantic and back in the span of a few minutes!
- The Sub-Mariner is the very first Marvel character, predating even Marvel Comics #1 (1939) ! He first appeared in Motion Picture Funnies Weekly (1939),
- For unexplained reasons, the Fantastic Four's uniforms have blue trim around the gloves and boots in this issue. They return to normal in issue #5.
- Mister Fantastic, the Invisible Girl, the Human Torch and the Thing all last appeared in Fantastic Four #3; They all appear next in Fantastic Four #5.
- The Sub-Mariner last appeared in TBD; He appears next in Tales of the Marvels: Inner Demons.
- Although Giganto was destroyed in this story, another Giganto appears in Fantastic Four: World's Greatest Comics Magazine #7.