Cliff diving’s marquee event thrilled spectators in Boston as the Red Bull Cliff Diving World Series made the 100th stop in its history. Participants plunged from up to 90 feet in the air from a waterfront art museum into the harbor below on Saturday. The Boston diving event is the only U.S. stop this year. The series wraps up in Sydney, Australia, in November. Organizers say that cliff diving attracts a special kind of athlete, especially when winning means leaping from an art museum into potentially frigid waters below. It was the third straight year that the popular spectator event has come to Boston.