Texas Water Safari

The Texas Water Safari is a boat race down waterways from San Marcos, Texas, to Seadrift, Texas. The total distance traveled is 262 miles. Racers must take all equipment needed with them, receiving only medical supplies, food, water, and ice along the way. The primary requirement is a boat powered only by human muscle. The event was first held in 1963, and is run annually. The race begins on the second Saturday of June of each year, barring bad weather.
In 1962 Frank Brown and Bill "Big Willie" George navigated from San Marcos to Corpus Christi without a motor. In 1963 they created the Texas Water Safari which would become an annual race.
Course.
The course includes natural rivers like the San Marcos, with rapids and dams. Most boats destroyed on the course are lost in the upper river. The San Marcos River converges with the Guadalupe River and becomes wider and slower. The main dangers in the middle river are sweepers, downed trees, logjams and dams. Near the end of the course there are lakes and swamps, and it ends with a crossing of the San Antonio Bay. Other challenges include alligators, sharks, water moccasin, fire ants, and mosquitos.
There are 11 checkpoints including the finish line. Their locations are published and they are staffed with officials. Each checkpoint has a cutoff time the racers must meet or be disqualified. The final cutoff time at the finish is 100 hours. The team captain of each team must be present at the checkpoint to sign off the team's time as the team leaves. Checkpoints: 
Records.
Athletes compete in classes. The Unlimited class has no restriction, except that the watercraft is powered only by human muscle, and restricted since 2006 to crews no greater than six. Attempts have been made to race craft of unconventional form, but the best results have been achieved by well-trained teams in crewboats.