The engine-room telegraph bell clanged. Almost immediately the Canvey increased speed. The mark-buoy bore abeam, a cable's length to starboard.
Crash! went the propelling charge.
Like a gigantic salmon-tin, the missile described its parabolic flight—so slowly that observers on the bridge could see the huge canister turning over and over in mid-air.
It struck the water with a resounding thud, flinging up a shower of spray. Already the Canvey under fifteen degrees of starboard helm was rapidly increasing her distance from the mark-buoy. Slowly the intervening seconds passed; so slowly that Broadmayne began to think the fuse of the depth-charge had proved defective.
Then came a truly stupendous roar. A slender column of water was hurled quite two hundred feet in the air. The hull of the Canvey shook under the terrific blast of displaced air. The tranquil waters of the bay were transformed into a mass of agitated waves.
The column of upheaved water fell with a loud hissing noise. For nearly half a minute the turmoil continued. Then, in the midst of the maelstrom, appeared a patch of calm, iridescent oil spreading steadily in all directions, while multitudes of fish, killed or stunned by the detonation, floated belly-upwards upon the surface.
"Away, diving-party," ordered Captain Raxworthy.
"With your permission, sir, I would like to accompany the divers, sir," said Broadmayne.
"Are you qualified?" asked the lieutenant-commander.
"Yes, sir," replied the Sub. "I did a diving-course at Whaley when I paid off from the Arcturus, and I've been down to fourteen fathoms."