Captain Marvel Jr #101 (1951)

Prof. Edgewise is telling a long boring story about Pharaoh Ra-Tep, an ancient Egyptian scientist of 7,000 years antiquity who he claims invented “things still unknown to our modern world” before mysteriously disappearing altogether. Freddy Freeman heads out to work as a meteor suddenly arrives in the sky, so Freddy calls CAPTAIN MARVEL to become Captain Marvel, Jr., catching the meteor to find it's a message in a bottle… from space and written in Egyptian! Flying into space to follow where it came from, he reads that it's from people marooned on “a sea in space” beyond Planet Pluto and soon finds the verdant, aquatic planet and a strange cloud of red coming towards him. He finds the water gives off a strange infrared radiation due to some kind of chemical in it and then hears a human scream and finds a large ship being attacked by a sea serpent. He manages to surprisingly easily pull off one of the creature's limbs, but finds they grow back pretty fast before he punches it in its soft stomach and it retreats. He finds that the ship is a trireme and the people aboard speak Egyptian and the crew describe this creature as an “Aquabus” and say they came there millennia ago via Pharaoh Ra-Tep, who created rocket fuel that allowed them to sail their ship in space and a special protective coating that keeps them from freezing in the vacuum of space. However, they're out of the fuel now and the protective coating has worn off with time, both of which only Ra-Tep knew how to make. Thus, they've been stranded there ever since. Junior dives to the bottom of the ocean to find that there is a strong weed that can be woven into an airtight covering for them, only to find the children are horribly despondent at the thought of leaving their “home” and don't regard Junior as one of them due to his mighty strength. To try to better appeal to them, he returns to being Freddy and suddenly feels a horrible fiery pain in his throat and falls over. The Aquabus soon returns and grabs the ailing Freddy, but when it tries to drag him into the water, he is revived enough to call CAPTAIN MARVEL to stop it again as Junior. This time, he ties its soft limbs together and throws it in to space and Junior reveals that this is the best he can do for them; if they returned to Earth, they'd fall into a coma from a lack of infrared radiation that they've lived with their whole lives (much like he did when Freddy collapsed.) The Egyptians decide that's for the best, since there's no more Aquabus to attack them and Junior returns to Earth. Later, Freddy tells the Professor that Ra-Tep was a great man indeed and Leroy is shocked that he's now interested in Prof. Edgewise's tales...