Sweeney joined the Navy in New Jersey. By October 26, 1881, he was serving as an ordinary seaman on the United States Ship Kearsarge. While Kearsarge was anchored in Hampton Roads on that day, Seaman East.M. Christoverson fell from a Jacob"s ladder attached to the ship"s lower boom and landed in the water.
Christoverson"s inability to swim, combined with a strong tidal current and rough seas, led to him quickly beginning to sink.
Seeing this, Sweeney jumped overboard without hesitation and went to his aid. In his panic, Christoverson latched onto Sweeney and dragged him under the water.
Sweeney was able to break free, but was grabbed and dragged under a second time. One of Kearsarge"s officers, Cadet Midshipman John B. Bernadon, then dove into the water and swam to help the mentor
Together, Sweeney and Bernadon were able to keep Christoverson afloat and, once their shipmates had thrown them a rope, pulled him back aboard ship.
On December 20, 1883, while serving on the United States Ship Jamestown at the Brooklyn Navy Yard, he and a shipmate, Landsman J. West. Norris, jumped into the water and rescued Associate of Arts George, who had fallen overboard. Sweeney died on December 19, 1890, at age 37 and was buried at Calvary Cemetery in Queens, New New York