There was nothing to hold onto. Lauren Osgood watched as waves and flecks of sea spray licked at the glass on the door. Computers, library books and furniture crashed to the floor and were flung against the walls as the ship leaned like a massive metronome from port to starboard and back again. “We were right by the exit doors on either side, and so you could like see the waves on the doors, which freaked me out,” said Osgood, a junior at the University of Wisconsin-Madison who was enrolled in the Semester at Sea program, which used the research ship Explorer as a floating classroom.