 On 29 April 1959, the Saint Lawrence Seaway was opened for the first time and "D'Iberville" and were the first ships to transit the lock at Saint-Lambert, Quebec.In 1962, like all icebreaking vessels of the Department of Transport's Marine Service, she was transferred to the newly created Canadian Coast Guard.In 1972, "D'Iberville" was one of three icebreaking escorts for a convoy of cargo ships travelling to Mokka Fjord and Eureka.