The aquamorph, Homo aquaticus, is one of the first genetically modified species of humans in the book Man After Man: An Anthropology of the Future., designed for life in the water, it lives in the marine environment of the earth in 200 years (the 22nd Century),

These beings had been created with the purpose of helping in the construction of underwater deuterium mills for fuel used for the interstellar colonization project due to the collapse of the human civilization. These are characterized by their modified paddle-shaped legs, which allow to swim, in addition to the change of the form of the head, which adjusts to be hydrodynamically efficient when swimming. The face is quite narrow, but broad at the sides, possessing only a couple of holes, rather centred eyes, large nostrils and a wide mouth. Due to the genetic modifications the Aquamorph is incapable of making facial gestures. Aquamorphs are able to breathe under the water by the use of gills that are located in the chest. They possess a high intelligence being similar to the one of their relative humans, able to use tools which carry in a special belt, 

Despite of not being able to reproduce, it seems that it is implied in the book that the experimentation with aquatic humans continued without problem even after completing the mission of interstellar construction or these survive and being able to survive underwater hundreds of years later, but in the end were replaced by aquatics, a posthuman species better adapted to the aquatic environment and able to reproduce.