(a) The purpose of the regulations in this part is to set forth simplified alternative marking schemes for those vessels operating in more than one service. Operating requirements for a given vessel could vary depending on the service, the season of the year, stability requirements, manning requirements and tonnage requirements. The conditions of assignment, restrictions applicable, form of the certificate and the load line marks are described.

(a) International service means:

(1) A voyage by sea between a port under the jurisdiction of the United States and a port of a foreign country, its colonies, territories, or protectorates, or conversely (a voyage exclusively on the Great Lakes is excepted); or

(2) A voyage that proceeds beyond 20 nautical miles from the territorial sea baseline.

(b) Great Lakes service means a voyage from a United States port or place on the Great Lakes to another United States port or place on the Great Lakes or to a Canadian port or place on the Great Lakes, or conversely. In concurrence with related Canadian regulations, the waters of the St. Lawrence River west of a rhumb line drawn from Cap de Rosiers to West Point, Anticosti Island, and west of a line along 63° W. Longitude from Anticosti Island to the north shore of the St. Lawrence River shall be considered as part of the Great Lakes. In addition, the Victoria Bridge, Montreal, Canada, is the dividing line between fresh water and salt water in the St. Lawrence River.