Nearer and nearer, louder and louder, sounded the melancholy note, just west of south. Both boys strained their eyes.
"I see it!" cried Percy, triumphantly. "There—rising on that swell! Almost astern! It's striped red and black!"
But Jim gave him no heed. Lips parted and face pale, he was gazing intently at something farther off. Suddenly he lifted his hand.
"Listen! Do you hear that?"
Above the noise of the surrounding sea rose a low, savage roar. Percy caught Jim's alarm.
"What is it?"
"The breaker on the shoal! Sometimes it combs up high as a house. It's less than a quarter-mile southwest of the buoy, and we're drifting straight down upon it! If we go over it, we'll be swamped, sure as fate, drug or no drug! We'll simply be buried under tons and tons of water!"
Percy fought off his panic.
"What shall we do?" he stammered.
"Make the whistler—if we can. It's buoy or breaker, and mighty quick, too!"