Nartec

The Nartec are a ocean-dwelling race of amphibious fish-men native to Earth.

Biology
Originally descendants of an ancient race of man that lived on a island in the Pacific Ocean, the Nartec were altered by long-term exposure by radioactive narna rocks, mutating them at a rapid pace within a few centuries to develop amphibious qualities.

They are humanoids, with huge orange eyes, blue-slippery skin and webbed hands and feet for hydrodynamic performance. The Nartec possess a dual respiratory system, retaining human lungs and gills on their necks in order to filter oxygen from the water. The Nartec are fast and fluid in the water, but are weak and slow on land.

The Nartec are a dying race. The radioactive rocks that had ensured their survival, also sealed their doom. The population and life span of the Nartec have dropped over an unspecified amount of time. Infant mortality has been rising as a result of birth defects. The dropping population has forced the amphibian race to inbreed, causing dangerously low fertility. The doomed Nartec have resorted to desperate measures to survive such as extracting DNA and organs from surviving humans and implanting them into their people.

History
The Nartec dwelled in a giant cave under the ocean off the coast of the West Coast. According to their history the Nartec once lived on 'the Surface', on an island in the 'Great Ocean.' However as the sea began to swallow up the island, over the decades the islanders built a towering wall around the island to protect them. The wall grew until it eventually became a dome and was completely submerged under the sea. Though according to Ax, this story is highly dubious.

When Visser Three developed the Sea Blade to locate the Pemalite ship in Earth's seas, the Animorphs engaged Visser Three as orcas. The Sea Blade was damaged during the fight, in the commotion a Nartec raiding party captured the Sea Blade bringing it to their home. Visser Three Hork-Bajir were captured and dissected by the Nartec and their corpses converted to stuffed mannequin.

The Nartec realizing the Sea Blade was a powerful new vessel from a new culture decided to use the ship to attack the Surface to escape their watery world that was slowly killing them.

Their plan never came to fruition when Visser Three and the Animorphs allied with each other to escape the Nartec with the Sea Blade.

Culture
The Nartec culture appears deplorably backwards. The Nartec are scavengers, salvaging wreckages and articles from shipwrecks over the millennia. Most Nartec technology is wholly dervived from stolen human technology. However, they have developed a technique of extracting human DNA for reproduction.

Nartec society is feudalistic; The royal class and aristocracy live in the centre of the town. The bourgeoisie live further out, while the traders, artisans and manufacturers live closer to the outskirts. Finally, criminals and the poor make out an existence outside the town.

Source

 * Animorphs #36: The Mutation