Southack, born in England, followed his father's footsteps as a naval man. As a young boy he went to sea. At the age of ten he was to gain first hand sea-battle experience. At age 23 he was to come to Boston and entered into the service of the colony of Massachusetts.
In 1690, Southack, as part owner and captain of the man-of-war Mary, was hired to join the Phips expedition against Port Royal. The taking and the sacking of Port Royal in 1690 was just the kind of work which apparently appealed to Southack. He was to come up the coast on raids on Acadia at least two other occasions: 1704, under John March, and 1707, under Benjamin Church. Though he did not accompany Walker in his aborted mission against Quebec in 1711, Southack was very active in the planning stages (he had developed quite a reputation as a cartographer).
Though Boston was always to be Southack's home base (he married Elizabeth Oakley and they had 11 children) he played a significant role in the administration at Annapolis Royal; in April of 1720, he was appointed to the first council of Nova Scotia. Right along Southack keep up his trading and fishing activities along the coasts of Nova Scotia.