The Texas Water Safari is billed as the “World’s Toughest Boat Race.” It’s been held every year since 1963, beginning at the headwaters of the San Marcos River on the second Saturday in June, and winding up a hundred hours later in San Antonio Bay. That’s 260 miles. That’s also completely insane. The boats have to be powered exclusively by human muscle, and participants must pack in everything they need. They can get water, ice and medical supplies along the way, but that’s i