Gigant #2/1978

In the underwater depths, Aquaman, Mera, and their son Arthur Jr. seek refuge in the Aquacave after being exiled from Atlantis. When Aquaman and Mera are captured by Toxxin, leader of a reclusive sea people, they're drawn into a desperate belief that a massive, mysterious plant is poisoning their world—and that only Mera’s sacrifice can save it.

In "null," Superman and Batman send the super-sons on an expedition to a newly discovered Mayan city in the Yucatan, accompanied by Prof. Hanson and his son. There, the group encounters the city’s two mysterious inhabitants, who hold a secret link to the professor that begins to unravel as the journey unfolds.