In 1946, following the end of World War II, a group of Coast Guard reservists formed the Marine Navigation and Training Association, Inc., MANATRA, in order to provide an opportunity for retired or discharged military and merchant marine personnel to practice seamanship and leadership skills aboard a vessel.
Applying to the Navy for consideration under the Navy's excess equipment program, the group went to the Brooklyn Navy Yard and acquired a 110-foot Navy submarine chaser in bad condition. Using their own skills, and the skills of ex-Navy and Merchant Marine volunteers who joined the group, the vessel was brought to seaworthy condition and named MANATRA I.
During these early years, the vessel was docked on the North Branch of the Chicago River, eventually moving to the old Randolph Street Naval Armory which was, at that time, just south of the locks on the Chicago River.
In the 1950's, members began to bring their children aboard. Some of these young people were members of the Sea Scouts or Boy Scouts, and those groups began to develop an interest in MANATRA. A Sea Scout group chartered the vessel for a week in 1963 and the relationship with Sea Scouts began to become more formal.
During the 1960's , MANATRA ran eight-day cruises from Chicago to Mackinaw Island for members and Sea Scouts, using the trips for training in seamanship, watch standing, navigation and leadership and teamwork. About twenty young people were aboard each voyage.