To blank out the world. That’s how my fellow passenger Lauren explains what drew her to cruise North America’s Great Lakes, the series of interconnected freshwater lakes – Superior, Michigan, Huron, Erie and Ontario – that straddle Canada and the mid-eastern United States.

In Lauren’s kitchen is a whiteboard etched with a map of the world. After visiting a location, she erases it from the board. The lakes remain as black outlines; shapes she’s not yet explored. Until now.