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.