Six in the morning on the bay is cold in a way you cannot prepare for. It wakes up every part of you at once, whether you asked it to or not.
People train for this one all year, and not because it is the hardest. It is because the course reads like a love letter to the city. You swim past battleships anchored here longer than you have been alive. You bike through Point Loma with the ocean on one side and the white crosses of Rosecrans on the other. You run the waterfront while strangers ring cowbells for you specifically. Olympic, sprint, relay, aquabike, duathlon, aquathlon, and a run for the people who came to cheer and could not sit still.
The transition area smells like neoprene and sunscreen, and registration is online.
The finish line is where people cry for reasons they cannot explain. Go stand at one once and you will understand it.