One of many small tugs built for the U.S. Army during and following World War II, the ST-2168 was built in 1954 by the Roamer Boat Company. She was transferred to the U.S. Army Corps of Engineers in 1962 and renamed Thunder Bay. The Thunder Bay was retired in 2002 and sold to Basic Marine of Escanaba, MI, who rebuilt the tug and renamed it Krystal.
Krystal is used around the Escanaba yard by Basic along with their other small tug, the Escort.
- Type: Single Screw Tugboat
- Year Built: 1954
- Builder: Roamer Boat Co., Holland, MI
- Hull No.: 22
- Horsepower: 310 bhp
- Length: 45′ 02″
- Breadth: 12′ 08″
- Depth: 6′ 00″
- Port of Registry: Escanaba, MI