Origin

Doctor Dorcas came in contact with Todd Arliss, a former Olympic swimmer who'd been injured and was now unable to swim. Dorcas promised Arliss a cure, though he told Arliss the demands would be high and transforming him into the superhuman Tiger Shark. Dorcas formed an alliance with the Atlantean warlord Krang. Krang provided his follower Orka as a test subject and Dorcas endowed Orka with the powers of a killer whale. Krang and Dorcas used Orka and a fleet of killer whales to attack Atlantis, but were thwarted by Namor and interference by Tiger Shark. 

Creation

Dr. Dorcas was created by Roy Thomas and John Buscema in 1968 and first appeared in Sub-Mariner # 5. 

Mayor Story Arcs

Namor

Dorcas later formed a secret alliance with Byrrah and Krang in a plot to keep Namor from being crowned prince of Atlantis. Namor captured Dorcas and Krang, who revealed Byrrah’s involvement in the plot, thus ruining his bid for power. He later, along with Attuma and Tiger Shark captured Hydro-Base and took Namor prisoner there. Namor regained his freedom with the help of the Hydro-Men and attacked the conspirators, throwing Tiger Shark into one of Attuma’s war machines. As Dorcas was able to fire a lethal blast from his hand weapon at Namor, the machine toppled on top of Dorcas and crushed him to death.

Thunderbolts

Years later, it was revealed that Dorcas survived by having injected himself with regenerative starfish DNA, and he'd developed an obsession with Songbird, intending to make her his slave.