From Dragon Ball Encyclopedia
Captain Dock (ドック, Dokku; FUNimation "Captain Dark") is a high ranking officer in the Red Ribbon Army.
Dock was a soldier in the Red Ribbon Army and a subordinate to General Blue when he made an appearance early during the General Blue Saga. While he went by the title of lieutenant in his first appearance, it is likely that the title of captain by which Dock was referred to in his second appearance is more accurate. He was obese, which Blue disapproved of, and carried a whip, which he used to enforce his very strict mannerisms. Still, Dark was shown to be fairly easy-going, which resulted in his being the first in the Blue Corps to be defeated.
When Blue split his unit into two "companies", Dock was granted control of Company B. His team traveled over the ocean to Kame House where their mission was to capture Turtle Hermit and confiscate one of the Dragon Radars that they were under the impression he had invented (although this achievement goes to Bulma Brief). When Dock asserted that he could not divulge any information or the Dragon Radar through Turtle Hermit, he prepared to use force, cranking his whip, but unaware that Turtle Hermit was a professional martial artist and one of the strongest Humans alive. Dock was soon defeated with a single punch to his stomach and Company B's defeat followed soon thereafter.
Dragon Ball GT
Along with countless other villains, Dock made a cameo appearance during the Super 17 Saga when the residents of Hell who had escaped to Planet Earth had to return back to Hell in "Piccolo's Best Bet".