This large tug was built in 1956 by John I. Thornycroft & Company Limited as the Atherfield for Red Funnel Tugs of England. In 1971, she was acquired by Atlantic Towing Limited of Saint John, NB and renamed Irving Hemlock. She was repowered in 1987. In the 1990s, the Irving Hemlock was transferred to Harbour Development Inc. She was renamed Swellmaster in 1996.
Serving as the lead tug for Harbour Development, the Swellmaster can be found all around eastern Canada, towing dredging equipment between ports and working on local dredging jobs.
- Type: Twin Screw Tugboat
- Year Built: 1956
- Builder: J.I. Thornycroft & Co. Ltd., Southampton, England
- Engines: 2 Caterpillar D398
- Horsepower: 2,040 bhp
- Length: 102′ 04″
- Breadth: 27′ 02″
- Depth: 10′ 01″
- Port of Registry: Saint John, NB