Meranno alias the U-Man was a frequent adversary of Namor the Sub-Mariner. Meranno was a member of the Homo mermanus species, also known as the Atlanteans. A research scientist in Atlantis, he was banished from the realm by Namor for wanting to betray them to Nazi Germany. Filled with a burning desire for revenge against Atlantis' ruler, Prince Namor, Meranno renamed himself U-Man (or, Unter-Wasser Mann) and joined the Axis Powers to fight Namor and his allies, the Invaders. Meranno used Nazi scientific procedures to augment his natural abilities, making himself much stronger than the average Atlantean and enabling himself to survive on the surface for extended periods of time.
His first battle with Namor as U-Man came when he kidnapped Betty Dean and attacked a plane carrying Winston Churchill to the United States. He was defeated when the Invaders intervened, but managed to escape.
A Japanese spy called Lady Lotus used her psychic powers to control Meranno, Master Man, Baron Blood, and Warrior Woman, and made them into the villainous team known as the Super-Axis.Later, Meranno allied with another Atlantean malcontent, Attuma, in an attempt to conquer the surface world. He has recently appeared in the new Invaders series, along with Warrior Woman. It was revealed that Meranno raped Lady Lotus and fathered her daughter, Nia.
Meranno possesses various superhuman physical attributes common amongs the people of Atlantis, though some of his powers are considerably more developed than the majority of his race.
Amphibious Physiology: Unlike most Atlanteans, Meranno can not only survive underwater but he can also survive on land for an unknown period of time without suffocating. While he can't survive on land indefinitely, it is known that he can remain on land without a breathing apparatus for more than 20 minutes. Like all other Atlanteans, Meranno's natural habitat is the water and his body is specially adapted to enable him to survive underwater. He has gills that allow him to extract oxygen from water and his vision is specially developed to see the Green end of the spectrum, enabling him to see perfectly even in the murkiest depths of the oceans. Meranno's physiology also allows him withstand extreme changes in water temperature and his blood circulation allows him to withstand extremely cold temperatures typical of great ocean depths.
Superhuman Strength: Like all Atlanteans, Meranno is superhumanly strong, though much more so than most Atlanteans. While on land and dry, Meranno can lift about 40 tons. In his native element, or if he is at least wet, he is somewhat stronger and can lift about 50 tons.
Superhuman Speed: Meranno can run and move at speeds superior to that of the finest human athlete. Meranno is also a much faster swimmer than the finest human athlete, and most Atlanteans for that matter. Whereas most Atlanteans can swim at speeds of up to 30 miles per hour, Meranno can reach speeds of 60 miles per hour.
Superhuman Stamina: Meranno's Atlantean musculature produces considerably less fatigue toxins during physical activity than the musculature of a human being. While in water, or at least wet, Meranno can physically exert himself at peak capacity for about 24 hours before the build up of fatigue toxins in his blood begins to impair him. The longer he is dry, however, Meranno's physical stamina rapidly diminishes.
Superhuman Durability: Meranno's body is much harder and more resistant to injury than the body of a human being. Meranno can withstand powerful impact forces, exposure to temperature and pressure extremes, and high caliber bullets without being injured.
Superhuman Agility: Meranno's agility, balance, and bodily coordination are enhanced to levels that are beyond the natural physical limits of even the finest human athlete.
Superhuman Reflexes: His reflexes are similarly enhanced and are superior to those of the finest human athlete.