University of Virginia senior Casey Schulman spent the past 14 weeks on a once-in-a-lifetime adventure with the school’s Semester at Sea program. The 22-year-old Falls Church native visited London and Portugal, Africa and the Amazon. This week, finally, she was scheduled to return home. On Saturday, during the ship’s final stop on the Caribbean island of Dominica, Schulman and other students took a break to go snorkeling. As she swam in the pristine tropical waters, a small boat backed into Schulman, killing her.