SANTA CATALINA ISLAND, Calif. — When the gun went off, I was near the back of the pack, wedged in a crush of over 250 runners. Some were tethered together. Most were jogging slower than I had anticipated. My goal: Don’t come in last.

For the first mile, I slalomed between competitors as we navigated a rutted dirt road pocked with divots large enough to roll an ankle. Later, we arrived at the first of our run-swim transitions. I zipped my wet suit, slid my pull buoy into place, pulled my mask over my face and dived into the cold sea. I had one comforting thought: Finally, I’m not the only one swimming in shoes.