CHAPTER PAGE I. THE TASK OF THE ALLIED NAVIES 17 II. THE NEW NAVY--TRAINING AN ANTI-SUBMARINE FORCE 36 III. A NAVAL UNIVERSITY IN TIME OF WAR 47 IV. THE NEW FLEETS IN BEING 50 V. THE HYDROPHONE AND THE DEPTH CHARGE 70 VI. SOME CURIOUS WEAPONS OF ANTI-SUBMARINE WARFARE 85 VII. MYSTERY SHIPS 96 VIII. A TYPICAL WAR BASE 102 IX. THE CONVOY SYSTEM 116 X. THE MYSTERIES OF SUBMARINE HUNTING EXPLAINED 126 XI. THE MYSTERIES OF GERMAN MINE-LAYING EXPLAINED 143 XII. THE MYSTERIES OF MINESWEEPING EXPLAINED 157 XIII. THE MINE BARRAGE 179 XIV. OFF TO THE ZONES OF WAR 187 XV. A MEMORABLE CHRISTMAS 192 XVI. THE DERELICT 202 XVII. MINED-IN 209 XVIII. THE CASUALTY 220 XIX. HOW H.M. TRAWLER NO. 6 LOST HER REFIT 226 XX. THE RAIDER 233 XXI. THE S.O.S. 238 XXII. IN THE SHADOW OF A BIG SEA FIGHT 248 XXIII. A NIGHT ATTACK 258 XXIV. MYSTERIES OF THE GREAT SEA WASTES 264 XXV. FROM OUT THE CLOUDS AND THE UNDER-SEAS 273 XXVI. ON THE SEA FLANK OF THE ALLIED ARMIES 286 INDEX 301 List of Illustrations SURRENDER OF THE GERMAN SUBMARINE FLEET _Frontispiece_ FACING PAGE PLAN OF A 55 FEET COASTAL MOTOR BOAT 16 LARGE HEAVILY ARMED GERMAN SUBMARINE 32 MOTOR LAUNCH HULLS BEING CONSTRUCTED 56 A 40 FEET COASTAL MOTOR BOAT AT FULL SPEED 64 ANOTHER VIEW OF THE SAME BOAT AT FULL SPEED 64 DROPPING DEPTH CHARGES 80 INNOCENT-LOOKING BUT DEADLY 96 HIDDEN TORPEDO TUBES OF H.M.S. _HYDERABAD_ 96 AFTER-DECK OF THE _HYDERABAD_ (BEFORE ACTION) 104 AFTER-DECK OF THE _HYDERABAD_ (PREPARED FOR ACTION) 104 MOCK WHEEL AND COMPASS PEDESTAL OF THE _HYDERABAD_ 112