Aquaman's first origin story was presented in flashback from his debut, narrated by the character himself:
“ The story must start with my father, a famous undersea explorer — if I spoke his name, you would recognize it. My mother died when I was a baby, and he turned to his work of solving the ocean's secrets. His greatest discovery was an ancient city, in the depths where no other diver had ever penetrated. My father believed it was the lost kingdom of Atlantis. He made himself a water-tight home in one of the palaces and lived there, studying the records and devices of the race's marvelous wisdom. From the books and records, he learned ways of teaching me to live under the ocean, drawing oxygen from the water and using all the power of the sea to make me wonderfully strong and swift. By training and a hundred scientific secrets, I became what you see — a human being who lives and thrives under the water. ”
Talk about "Sunken Cities"!