The Diomede Islands of the Bering Strait are a world apart, though only 2.4 miles separate them. Little Diomede belongs to the United States, Big Diomede to Russia, and the international date line runs between them.

So when Lynne Cox swam between them in 1987, she set a peculiar endurance record: Though the waters were cold enough to kill an average swimmer in 30 minutes, she departed “Yesterday Isle” at 1 p.m. on a Friday … and arrived safely on Tomorrow Island on Saturday.