Dead reckoning, one of the oldest and most basic methods of navigation, was for centuries an essential piece of the mariner’s skill set, and it was still required to captain a charter sailing boat in the late 1990s, when the idea of a late summer week on the water off the San Juan Islands first captured my imagination. The islands, hundreds of them, some inhabited and others no bigger than a pickup truck, form an archipelago off the northernmost coast of Washington and British Columbia. On the water, you share the Salish Sea living room with the likes of baleen whales and orcas, sea lions and otters. The sky is just as lively by day, with the sea birds monitoring the waters for their next meal, and at night – the silent, spectacular sea of twinkling stars.

I learned to sail when I was a kid, growing up near the water in Southern California, where skiffs were common. My great-uncle Fred taught me the ropes, but not the dead reckoning system using compass, landmarks, and coordinates of time and speed to chart your course.