Just before sunset, U75, having made the passage unobserved, brought up in twelve fathoms of water, resting evenly on the firm, hard sands at the bottom.
Ross and his chum turned in early. There was nothing for them to do. They held aloof from the crew; there were no books to entertain them, no games to amuse them. The submarine was now motionless, sufficient water ballast having been taken in to allow her to settle firmly upon the bottom; but, in order to be prepared, the anchor was let go. Thus not the slightest movement of the hull was apparent. The rest, after hours of erratic movement on the oily swell, was a welcome one.
The lads had set their joint watch by the submarine's time, which, being mid-European standard, was one hour fast of Greenwich.
For several hours they slept soundly and undisturbed. Suddenly they were both awakened by the muffled tramp of men in heavy sea-boots. The solitary light in the alley-way was switched off; the water-tight doors were firmly closed. Already the air in the confined space was stifling.
"What has happened?" asked Vernon anxiously, for the vessel, instead of resting immovably upon the bed of the channel, was now rolling sluggishly. Yet she could not be under way, for the motors were silent.
Springing from his bunk, Ross felt for the switch of the electric light. It was already down, yet the flow of current was interrupted.
"Let's find out," he said. "Come along."
The lads, before turning in, had carefully laid out their clothes, so as to be ready to slip into them at a moment's notice, yet it was a matter of considerable difficulty to dress in the dark.
"The door's closed," announced Ross as the lads groped their way to the end of the alley-way.
"I believe the submarine's holed," suggested Haye.
"No; she wouldn't lift as she's doing. Besides, the crew are moving about. Let's bang on the door with our boots."
For several minutes they hammered, but without result. The air, never very fresh, was now almost unbearable, owing to lack of ventilation. The imprisoned youths began to get desperate.
Then, without warning, the door slid back. The alley-way was flooded with brilliant light.
"Make haste!" shouted a voice which the lads recognized as that of Hans Koppe. At the same time he grasped Ross by the shoulder and literally dragged him across the steel threshold. Vernon followed quickly, but barely had he gained the compartment beyond than the massive steel door shot back again.
"Didn't you hear the order all hands for'ard?" asked Hans, not unkindly, for the white faces of the English lads told their own tale.
"No," replied Ross. "Besides, we are not included in the 'hands', are we?"
"You'll have to bear the consequences if you don't obey," rejoined Koppe. "I'm supposed to be looking after you, but how was I to know you hadn't turned out? Fortunately for you, I heard your knocking, and asked Herr Kapitan to open the doors. He was angry, but did so."
"What has happened then?" asked Trefusis, for the seaman seemed in a communicative mood.
"A shift of wind. It's blowing great guns up aloft, and there's a terrific tumble into this channel. We've dragged, or, rather, swung round our anchor."
"But we are safe enough?" asked Vernon.
"Yes, safe," replied Hans. "Too safe; we cannot break out our anchor. They are sending a diver to see what is amiss."
Evidently the diving arrangements on board were not considered to be of a confidential nature, for Hans led the way to the compartment under the fore-hatch, without the lads being sent back by the significant word "verboten".
A man was preparing for a submarine walk. He was already dressed in an india-rubber suit, with leaden weights attached to his chest, back, and boots. Two others were standing by, ready to place the helmet over his head, when Leutnant Rix had finished giving him minute directions.
The officer spoke rapidly and in a low tone. Ross could not catch all he said, but the words "gefährliche Strömungen" (dangerous currents) and "Der Wendepunkt der Flut" (slack water) and "Drei Viertel funf" (a quarter to five) occurred frequently.
Vernon glanced at his watch. It was then a minute after four. Apparently Rix was impressing upon the man that he must clear the anchor at slack water, which occurred at a quarter to five.
The two attendants then proceeded to place the diver's helmet on his head. The lads noticed that it had neither air-tube nor telephone wire. Nor was there a life-line attached to his waist. Fresh air was obtained from a metal case strapped to his back. The man was able to work independently, and without having to rely upon his air supply from the submarine.
The oval door in the diving-chamber was thrown open. The diver entered, and the water-tight panel was quickly replaced. One of the seamen thrust over a short lever, and immediately water rushed into the small compartment. As soon as the space was filled the diver was able to open a similar door in the outer plating of the submarine, and thus gain the bed of the sea.
Presently Leutnant Rix turned, and saw for the first time that Ross and Vernon were discreetly standing in the background.
"Go away. It is forbidden!" he shouted angrily.
They obeyed promptly, retreating to the space allotted to the crew, since it was neither desirable nor possible to return to their bunks.
For some minutes the luckless Hans Koppe was subjected to a severe dressing-down by his hot-headed officer, and when at length the seaman rejoined the lads he was in no humour to resume conversation.
Slowly the minutes sped. The submarine was still rolling sluggishly, in spite of the fact that more water had been admitted into the ballast tanks.
The men were talking seriously amongst themselves. From scraps of conversation that drifted to the lads' ears, it was evident that they had grave doubts concerning the ability of the diver to perform his task, and even of his chances of regaining the submarine, owing to the violent disturbances of the water.
Presently the motion of the anchored submarine became more acute. A weird grating sound—the noise made by the hull rasping over the bed of the sea—was distinctly audible.
One of the seamen produced a pocket compass. His startled exclamation brought other members of the crew around him. The magnetic needle was apparently describing a semicircle. U75 was swinging round her anchor.
Just then a bell tinkled, and a disc oscillated on the indicator board on the bulkhead. Instantly the two men who had been told off as attendants upon the diver hurried aft, while their companions crowded expectantly around the door.
The two men came back, staggering under the weight of the diver. They had already removed his head-dress and leaden weights. Water dropped from his rubber suit. His face was livid, his eyes wide open and rolling. One of his bare hands was streaked with blood that flowed sullenly from a cut in his numbed flesh.
Kapitan Schwalbe and Leutnant Rix followed him into the crew-space. It was not through feelings of compassion that they had come for'ard. It was acute anxiety to hear the diver's report.
The luckless man was laid upon the mess-table. His attendants divested him of his diving-suit, and rubbed his body with rough towels. A petty officer poured half a glass of brandy down his throat.
"What is amiss?" Kapitan Schwalbe kept on repeating.
With a great effort the diver sat up.
"An anchor, sir," he gasped feebly. "An anchor—an English naval pattern one—has been dropped right over ours. A very big one."