Achak possesses the conventional attributes of Homo mermanus: gills that extract oxygen from water, superhuman physiology to withstand extreme pressures and temperatures, and acute vision. He can swim at approximately 30 miles per hour. He can remain out of water for approximately nine minutes before beginning to suffocate. However, he can operate on the surface by wearing a water-filled helmet or using a chemical that enables him to draw oxygen from the air.

Achak and his family were among the Atlanteans that settled in New Atlantis which exists beneath the mutant refuge known as Utopia.

Formerly New Atlantis

Stuart Moore, Ariel Olivetti

Waya (mother), Mato (father)