At first her commander had been ignorant of the unpleasant fact that he was towing a British picquet-boat in addition to dragging two mushroom anchors over the sandy bottom; but when he made the disconcerting discovery he altered his course and attempted to make for Zeebrugge. This he did blindly, since he dare not rise to show her periscope above the surface. By dint of careful helmsmanship the picquet-boat also turned and kept dead in the wake of her invisible tug. By this time a dozen steamboats belonging to the flotilla arrived upon the scene.
Presently the drag of the anchor made itself felt, for the bottom of the sea had changed from sand to stiff mud. Still ignorant of the nature of the obstruction, the German lieutenant-commander was under the erroneous impression that he had fouled the moorings of a mine. He therefore reversed engines and attempted to back clear of the entanglement.
The easing-off of the strain on the chain gave Tressidar warning. Promptly he ordered "easy astern," at the same time megaphoning his suspicions to the nearest steamboats.
Unprovided with explosive grapnels, the boats were unable to make an end of the submarine by detonating a charge of gun-cotton against her hull. The coup de grâce would have to be administered by a destroyer, and up to the present no attempt had been made by the boats to summon one to their assistance. Officers and men were thoroughly enjoying their novel duck hunt, and were in no hurry to finish the sport.
But when the submarine commenced to back astern the possibility of her disengaging herself from the toils became apparent. Quickly two picquet-boats dashed in opposite directions across her supposed track, each craft towing a stout grass-line astern, to which were attached lumps of metal in order to sink the otherwise buoyant fibre.
The operation was successful, for the rope, caught by the revolving propellers, wound round the shafting like coils of steel, until the electric motors were brought to a dead stop.
"That's done the trick," exclaimed the lieutenant gleefully. "We've collared the tin of sardines and now we'll have to wait for the tin-opener. What water have we?"
A cast of the lead gave eleven and a half fathoms with a bottom of mud mingled with shells and coarse sand. The submarine, finding herself disabled, had "sounded" and was resting on the bed of the sea.
"Suppose we couldn't hike her clear and tow her alongside the 'Anzac?'" hazarded Stephens, one of the subs. "A strain of the old ship's steam capstan would heave her to the surface in a brace of shakes. Pity to rip up the strafed hooker when we have a chance of collaring her intact, isn't it?"
"May as well try," replied the lieutenant, who was loth to destroy the craft that had given him a "run for his money." "Tide's rising. We'll lower a couple of bights of chain and see if we can shift her. I don't suppose she has a deadweight of more than a couple of tons—if that. Hulloa! The ball's opening."