Calvin is a fairly tall man with a dark brown skin-tone, brown eyes and no hair. However, after being experimented on by Black Manta he now possesses gills and webbed hands and feet. He wears a simple, skintight purple Atlantean garment. Around his waist is a lighter colored stripe like a belt. There is a stripe in the same color around the end of his sleeves, and over his shins as well.
Durham was originally one of Black Manta's henchmen. He was genetically engineered to become a water-breather to infiltrate and destroy Atlantis from the inside, but he forsook his mission when he met Sha'lain'a. They married, and he raised Kaldur'ahm as his son in the city of Shayeris.
Atlantean attributes:[nb 1] Atlanteans, although human, have through scientific and sorcerous means developed several abilities which allow them to live comfortably under the sea:
Underwater breathing: As a result of his experimentation, Calvin has gained the Atlanteans abilities of surviving the aquatic atmosphere under the sea. Some accomplish this without the presence of visible gills.
Temperature resilience: Resistant to low temperatures and the effects of freezing, although notably hindered by high temperatures.