This paper describes the design and construction of two small icebreakers for operation exclusively in the fast-flowing Niagara River above the celebrated falls. Special features of these purpose-built craft—which due to their dangerous operating environment include many redundant systems—are presented. Results of maneuvering trials and model tests are given, along with a comparison between hull forms of the two vessels—Ontario Hydro's Niagara Queen II and the William H. Latham, operated by the New York Power Authority.