"Off the Irish coast," replied his brother.
"Wish one of our destroyers would put in an appearance," remarked Leslie wistfully.
The sub made no audible reply. His views upon the matter, based upon actual experience, told him pretty plainly that the captain of a British war-ship would not be likely to ascertain whether there were compatriots on board the craft he purposed to destroy. Also, there had been fully authenticated cases of the Huns locking the prisoners down below before they abandoned the sinking ship. Sefton did not mind running legitimate risks in action, but he had a strong objection to being "done in" by British guns.
His reveries were interrupted by a shrill whistle from the conning-tower. Instantly the somnolent men were roused into activity. In less than thirty seconds Sefton and his brother were tumbled below, the decks were cleared, and the hatches closed.
By the inclination of the floor of the compartment that served as a cell Sefton realized that the U boat was diving. Almost at the same time there was a muffled detonation as a 12-pounder shell, fired from a destroyer at a distance of 7500 yards, exploded immediately above the spot where the submarine had disappeared.
"Good heavens, she holed!" ejaculated the sub, as the U boat quivered and dipped to an alarming angle. Momentarily he expected to hear, above the rattle of the machinery, the irresistible inrush of water and the shrieks of the doomed crew.
But in this he was mistaken. The nearness of the explosion of the shell had urged upon the submarine's kapitan the necessity for haste. Thrusting the diving-planes hard down, he caused the U boat to dive with unusual abruptness, never bringing the vessel upon an even keel until she had descended to a depth of twelve fathoms.
The rest of the day was passed in utter monotony as far as the prisoners were concerned. Although it was two hours before the U boat dared to expose the tips of her periscopes above the surface, the greater part of the day was spent in running submerged.
Towards evening U99 ascended, and, altering course, stood in pursuit of a small tramp. After a short chase, for the former had the advantage of 15 knots in speed, the submarine approached sufficiently near to be able to fire a shot close to her quarry.
Almost immediately the tramp slowed down and hoisted American colours. It did not take U99 long to range up alongside, and the unterleutnant and half a dozen seamen proceeded on board.