Built in 1976, by Burton Shipyard Incorporated of Port Arthur, Texas (hull #531) as the Leopardo Grande for Tidewater Marine Services Incorporated of New Orleans, Louisiana
In 2000, the tug was acquired by Seaforce Marine Incorporated of Norfolk, Virginia. Where she was renamed as the Portsmouth.
In 2005, she was acquired by the K-Sea Transportation Partnership of East Brunswick, New Jersey. Where she was renamed as the Norwegian Sea.
In 2006, she was outfitted with a JAK-400 coupler system. And, an upper wheelhouse at Feeney's Enterprises of Kingston, New York.
In 2011, the K-Sea Transportation Partnership was acquired by the Kirby Corporation of Channelview, Texas. Where the tug retained her name.
In 2017, the tug was phased out of active service. And, she was "laid up," at the Kirby Corporation's yard in Philadelphia, Pennsylvania.
Powered by two, sixteen cylinder, EMD diesel engines. Turning two, cast steel, fixed pitch propellers. She is a twin screw tug, rated at 3,900 horsepower.
Her electrical service is provided by two 99kW generator sets. And, a third, auxiliary 99kW generator set. The tug's capacities are 129,600 gallons of fuel, 8,100 gallons of lube oil, 122,400 gallons of ballast, and 12,310 gallons of potable water.