Aquaman had to learn what was Seaman’s story. The story soon established Seaman had the same water-based abilities as Aquaman and seem more skilled at them. The answer to the identity mystery was that Seaman was an alien. His spaceship had sunk into the ocean and he needed at least one more person with the same abilities. He helped Aquaman in an attempt to befriend him, not to show him up. He had to repeatedly flee to avoid a number of eager photographers which were following Aquaman.
The real name of Seaman was not given. Seaman just indicated his species, equivalent to “Earthman” for Aquaman. He came from a planet largely covered with sea. His abilities were generic to his race and his skills were the result of using him since birth.