Like the Peloran they were based on, the Arnam can survive on far less oxygen than most other Races of Humanity, granting them far greater endurance. The Arnam have half-sized lungs compared to most humans though, which pulls back much of that endurance. They can run or exercise far less than a Peloran when in air, and they are at a decided disadvantage to their cousins when in full combat. The half-sized lungs allowed the Albion to place a set of fully functional gills into the Arnam that allow them to breathe under water. They work in both fresh and salt water, making them capable of operating in the waters of most human-occupied worlds without needing breathing systems. That is where their true advantages come in, and most Arnam spend most of their lives underwater.