What's the difference between an ice-strengthened hull and an icebreaker hull?
The ship's purpose drives the difference in design. Icebreakers are designed to ride up onto ice, crushing it with the ship's weight. This opens a path for other vessels trying to navigate icy waters. A ship with an ice-strengthened hull can navigate in waters dotted with ice. It has neither the strength nor the weight to ride up and crush ice.
