Three or four miles away, and also within the limits of the bay, the Fisherton fleet was at work, the boats running under reduced canvas, with their heavy trawls trailing astern. In the bright sunshine their dark-tan canvas and white hulls made a pleasing picture, the warm colours contrasting vividly with the yellow cliffs and dark-green of the pine-woods fringing the bay. Far out to the southward could be discerned the squat form of a Blimp as it see-sawed five hundred feet above an up-channel tramp steamer--the solitary visible reminder that there was a war on, and that there were such things as U-boats lying in wait for British merchantmen. For the best part of an hour Derek exercised his crew, practising "man overboard"--the "man" being represented by a life-buoy thrown overboard at an unexpected moment--and also slowing down for the purpose of enabling the individual members of the crew to fix their position on the chart by means of cross-bearings. Suddenly the dull boom of a gun broke the stillness of the air. Derek, who was bending over the sight-vanes of the compass, raised his head at the familiar sound, although what seemed to be a long time had elapsed since he last heard the report of a quick-firer. To his astonishment he was just in time to see the masts and sails of one of the fishing-boats disappear over the side, to the accompaniment of a shower of spray and a cloud of smoke from the bursting projectile while less than four hundred yards away from its victim was a large U-boat. The pirate had evidently been resting on the sandy bottom of the bay, and finding that she was in the vicinity of a fleet of small and unprotected fishing-craft, had judged it a good opportunity for an object-lesson in kultur. A careful survey of the horizon by means of the periscopes had failed to reveal anything of a suspicious nature to the kapitan-leutnant of the unterseeboot. M.B. No. 1164 B, lying motionless on the water, was an inconspicuous object, her aviation-grey painted sides hardly visible against the haze on the skyline. The crew of the motor-boat looked enquiringly at their skipper. It never occurred to them that a hostile craft was in the vicinity. Not one of them had seen a U-boat except in the form of a picture in an illustrated paper, and this one did not resemble their idea of a German submarine. Derek weighed up the case in a few brief seconds. Here he was in a fast motor-boat with a raw, practically untrained crew, and with not so much as a pea-shooter on board. The Hun probably carried a couple of six-inch quick-firers and a few machine-guns. By force Derek could do nothing. Nor could he, with any degree of honour, seek safety in flight and leave the slowly-moving fishing-boats to the mercy, or rather the lack of mercy, of a ruthless pirate compared with whom the Buccaneers of the Spanish Main were gentlemen.