Suddenly there was a jerk; the launch quivered, and swung about.

“Oh! what was that?” demanded Miss Colton, shortly.

“The anchor,” I answered. “We have reached the outer shoal.”

“And,” hesitatingly, “shall we stay here?”

“Yes; unless—”

“Unless what?”

“Unless . . . Hush! listen!”

There was an odd rushing sound from the darkness astern, a sort of hiss and low, watery roar. I rushed to the bow and dragged the anchor inboard with all my strength. Then I ran to the wheel. I had scarcely reached it when I felt a hand on my arm.

“What is it?” asked the young lady, her voice quivering. “Oh, what is it?”

“Wind,” I answered. “There is a squall coming. Sit down! Sit down!”