It was no use denying that Derek fully realized his position. His sensations were somewhat akin to those on the occasion of his first solo flight, but with this difference. Then he was responsible for himself alone. If an accident had occurred through his inexperience or error it was he alone who would have suffered. Now he was directly responsible for the safety of five men with practically no experience of the ways of the sea, who looked to him implicitly, took their orders from him, and, in short, placed their lives in his hands. Added to this was the fact that he was answerable for the safety of the boat—a practically brand-new craft that had cost the nation a sum closely approaching £2000.

To port and starboard of the narrow channel were dangerous, unobtrusive sandbanks, studded with concealed ledges of rock, their presence indifferently marked by the milk-white rollers that lashed themselves in impotent fury upon the shoals. A slight error of judgment, a wrong turn of the helm, and the frail cockle-shell would almost certainly run aground, and be dashed to pieces in the breakers.

Derek quickly found that R.A.F. 1164 B—that being the official designation of his command—was decidedly wet. Her long, lean bows, and the weight of her engines being well for'ard, tended to make her shove her nose into it. Showers of icy spray flew inboard, enveloping the occupants of the steering-well, and making them duck their heads as they gasped for breath. Well it was that Derek and his crew were well equipped with oilskins and sea-boots; even thus protected moisture found its way down their necks, soaking chillily against their chests and backs.

Nevertheless it was wildly exhilarating. The rapid pulsations of the powerful motor, the rhythmic lift of the long, lean hull to the waves, the hiss and the sting of the flying spindrift, and the unwonted sensation of speed—a sensation not experienced when flying at a height—all combined to give a new zest to life.

And to what purpose? At first sight it was a mere joy-ride, a pleasure-trip in an expensive motor-boat at the cost of the British taxpayer. But it was part of a system of training. Since the amalgamation of the R.F.C. and the R.N.A.S. it was hardly the thing to continue to draw upon the hard-worked navy for sea-going craft to attend upon the rapidly-increasing fleet of coastal airships and sea-planes. And since the aerial-fleet is liable to accident, it is also advisable to have assistance promptly and efficiently. Hence the necessity for the formation of an auxiliary marine branch of the R.A.F., so that in the event of a "Blimp" or a flying-boat being compelled to "land" upon the sea, aid would be quickly forthcoming from the motor-boat about to be attached to the various sea-coast air-stations. And as soon as the officer under training at Sableridge had passed his period of probation in charge of a small craft he would be posted in command of one of those seaworthy vessels known as a "coastal M.L.", on board of which he would live an almost idyllic existence, sleeping and living in one of the most comfortable little ward-rooms imaginable.

At reduced speed M.B. No. 1164 B crossed the bar, wallowing and plunging in the confused cross-seas. But for the protection afforded by the after-canopy she might have fared badly, for green water was slapping viciously against the canvas covering on both quarters. Although wet, she was a good sea-boat, and, beyond a quantity of spray, she passed through her ordeal without shipping any dangerous quantity of water. Then, gathering way, she glided serenely over the long, oily rollers of the open bay.

Derek's orders were to cruise within the limits of Old Tom—a detached chalk pinnacle on the south-western side of Coombeleigh Bay—and Thorbury Head, a bold promontory on the eastern side. Here, with ordinary caution, a boat could come to little harm, the water being fairly deep, and unencumbered with rocks or dangerous currents.

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.