Endurance swimmer Diana Nyad stroked through the Florida Straits early Monday, trying to accomplish at 61 years old what she failed to do at 28: swim more than 100 miles from Havana to Key West. If she makes it to the Florida Keys after an estimated 60-hour swim, Nyad would become the first person to traverse the strait without the aid of a shark cage, relying instead on technology and divers to fend off the finned predators.