On a Viking cruise of the Great Lakes, comfort and adventure sail with science and submarines

Our pilot stood on the roof of the yellow submarine named John, floating beside a Lake Superior islet where cliffs rise straight from the water and end in a shock of pines.

Six passengers from the cruise ship Viking Octantis approached on an inflatable Zodiac motorboat. One by one, we climbed on top of the sub, then down the hatch into a submerged cockpit. I took my assigned seat and gazed out the panoramic windows. Today the waters of this big, cold lake, which are often crystal-clear, glistened with an opaque aquamarine.

The passengers, who had been together for the past six days on a Viking cruise of the Great Lakes, laughed nervously, remembering a casual line from the submarine safety video: "If the pilot becomes unconscious, press the green button." I eyed the green button, just below the controls.

We wouldn't be needing it.

The pilot, Philip, relayed our location to Octantis and filled the diving tanks with water, as the sub slipped below the surface. We gently descended, ever deeper into the turquoise abyss. At some 130 feet, Philip activated the thrusters and navigated to the base of a rock wall. I realized that Pyritic Island far above us was merely the tip of a tall sea stack. We were now at the bottom of it and I was glimpsing the world's largest freshwater b....

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