For four decades, Nancy Hemmingway and Elizabeth Whitney have organized the annual Transbay Swim on the Sunday after Labor Day—at least as much as a word-of-mouth, unpublicized, unsponsored event on publicly-owned land can be considered organized.
But this year, Ms. Whitney and Ms. Hemmingway say they are retiring the early-morning swim—which, according to their count, drew over 100 people last year—due to safety concerns as well as the fear that its homegrown character is vanishing.
“The message…