Built in 1973, by McDermott Shipyard Incorporated of Morgan City, Louisiana (hull #181) as the Ocean Sun for L and L Marine Services Incorporated of St. Louis, Missouri. A subsidiary of the Apex Oil Company of St. Louis, Missouri.
In 1988, the tug was acquired by the Morania Oil Tanker Corporation of Staten Island, New York. Where she was renamed as the Morania No. 3.
In 1994, she was acquired by Penn Maritime Incorporated of Stamford, Connecticut. Where she was renamed the tug as the Dolphin.
In 2000, the Morania Oil Tanker Corporation merged with Penn Maritime Incorporated of Stamford, Connecticut. Where the tug retained her name.
In 2012, Penn Maritime Incorporated 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.
In 2018, she was acquired by the Curtin Maritime Company of Long Beach, California. Where the tug was renamed as the Karen C.
Powered by two, twelve cylinder, EMD 12-645-E5 diesel engines. Turning two, cast steel, fixed pitch propellers. She is a twin screw tug, rated at 4,300 horsepower.
Her electrical service is provided by two, 75kW generator set. The tug's capacities are 120,727 gallons of fuel.