Marilyn Grace Bell Di Lascio is a Canadian retired long distance swimmer. She was the first person to swim across Lake Ontario and later swam the English Channel and Strait of Juan de Fuca.

Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north, west, and southwest by the Canadian province of Ontario, and on the south and east by the U.S. state of New York. The Canada–United States border spans the centre of the lake.