Bay-class icebreaking tug
(重定向自Icebreaking Tug)

The USCG Bay-class icebreaking tug is a class of 140-foot (43 m) icebreaking tugs of the United States Coast Guard, with hull numbers WTGB 101 through to WTGB 109.
They can proceed through fresh water ice up to 20 inches (51 cm) thick, and break ice up to 3 feet (0.91 m) thick, through ramming. These vessels are equipped with a system to lubricate their progress through the ice, by bubbling air through the hull.