The Aquans are a sapient humanoid species which inhabit the oceans of planet Argo. Once a land-based species with advanced knowledge of medicine and genetics; they were forced to purposely mutate themselves to develop gills when global-scale earthquakes shook the planet and caused entire continents to sink, turning Argo into an oceanic world.
The Aquan civilization is governed by a Ruling Tribunal which enforces strict laws against visiting the old land cities. They also prohibit the capturing of the Sur-Snake, an animal whose natural toxins are capable of reversing the Aquan mutations.