4 a.m.
Frank snapped his binoculars on a bobbing black spar . `` Buoy and fishnet , '' he decided after a quick scrutiny . Frank kept the late watch that night . At 4 a.m. he turned in . At five he climbed hastily from his bunk at the jingle of general alarm , and reached the bridge on the run in time to see the exchange of recognition signals with a British man-o ' - war , which vessel had run into a submarine while the latter was on the surface in a fog . The warship had just rammed the U-boat . `` Can we help you ? ''