Dull in imagery and contrast With the coming of spring, ice-breakers push out into the frozen St. Lawrence, river, to clear the channel for shipping. MLS - Federal Ice Breaker, MB McClain breaking ice. CUS - The bow of the ice breaker. MCISL - The McClain going through the ice. CULS - The McClain runs into some thick ice, so it backs up, and full speed ahead breaks through the ice