Tyson Bottenus once captained an 80-foot schooner called the Aquidneck . He sailed tourists off the coast of Newport, R.I., discussing the area's history and sites. In January 2018, he had finished another season at the schooner's helm and had recently gotten engaged to his partner of many years, Liza Burkin. To celebrate, the couple, avid cyclists who've ridden through New Zealand and Japan, set off for a bike tour of Costa Rica. "We were on this very, very dusty road for a long time," Bottenus remembers of a ride to Montezuma on the Nicoya Peninsula. "It was a dirty, sandy, hard-packed road." While going downhill, Bottenus crashed, badly scraping his elbow. The next morning, a doctor spent about an hour picking out little rocks and cleaning dirt from the wound before she bandaged it up. The injury kept him from swimming but otherwise didn't disrupt the trip. About a month after returning to Rhode Island, Bottenus started having head...