The Neptunians are an amphibious race that live in a secret underground society. One of their ancient ancestors was a hero known as the Fin, which their legends spoke would one day be reincarnated and live among them again as their champion. In 1941 Peter Noble was a Navy officer who was caught in a sinking submarine and was shocked to find that the immense pressure and lack of air did not kill him. He discovered an undersea civilization called Neptunia. Defeating their leader, Ikor, in a battle to the death, the Neptunians believed that Noble might be the reincarnation of their savior, the Fin. Noble then made a costume and became a costumed adventurer, taking up the alias of the Fin.
- 1 Appearances of Neptunia (Underwater City)
- Minor Appearances of Neptunia (Underwater City)
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- Location Gallery: Neptunia (Underwater City)