"All secure!" he spluttered. "Let's hope the buoy won't bump before we're well away. Strike out, Peter." Both swam their hardest. Breathlessly they clambered over the yacht's side, and without loss of time the _Puffin_ gathered way and drew clear of the danger zone. Peter and his Scoutmaster went below to dress. As soon as possible they regained the cockpit. Brandon was keeping the yacht tacking at about a quarter of a mile from the square of red bunting that indicated the position of the now invisible menace. "Now for a little signal-practice," said Mr. Grant briskly. "Where's the Code Book. Let's hope our letter B won't be required." The _Puffin_ was within visual signalling distance of Dungale coastguard station. Her signal, reporting the presence of a floating mine was seen and acknowledged. "We may as well hang on and see the fun," observed Mr. Grant, and the suggestion met with unanimous approval. Within half-an-hour the fishery protection gunboat appeared upon the scene, and the highly interested Sea Scouts watched the proceedings with zest. The gunboat opened fire with rifles and a machine-gun. The red signal flag disappeared as if by magic. All around the spot the water was churned by the hail of bullets. Yet the mine did not explode. "Probably a dud," commented Brandon when the firing ceased. "They've sunk it, more than likely." But after a brief interval the gunboat reopened fire. Suddenly a huge column of water was flung high in the air, to be followed almost immediately by the terrific crash of the explosion. "Good-bye to our beaker, boathook and signal-flag," remarked Peter. "Lost in a thundering good cause," added the Scoutmaster gravely. "Now, lads! up helm. We've got to look slippy if we're to save our tide!" CHAPTER VI TO SCUTTLE HIS SHIP "I DON'T understand, sir," stammered Captain Josiah Quelch, fumbling with the peak of his cap. "You don't understand," repeated Mr. Fiandersole, head of the shipping firm that bore his name. "You don't understand, eh? Do you want me to put the proposition any plainer? I don't think there's need for that, Captain Quelch." There was silence for a few moments. Through the heavily curtained door of Mr. Fiandersole's private office came the clicking of half a dozen typewriters. "It's no use trying to hedge," continued the head director crisply. "You've got to do and do it promptly--this voyage, in fact. I needn't recall to your mind a certain incident----" "No, sir, you needn't," rejoined the agitated captain. "You've got me fairly on my knees." "And I jolly well mean to keep you there!" snarled Mr. Fiandersole. "After all's said and done, you benefit. Play me false and you'll get seven years on that other count. And you can't round on me, Captain Quelch. What passes between us is without witnesses, and my word is as good as yours--better, if it comes to a court of law." "But my certificate, sir," protested the other.