But when the _Coquette_ got around to the side of Gannet Island where the boys' camp was established, the shadow of the high, wooded ridge was thrown out so far across the lake that the swimming raft and its neighborhood were in darkness. The catboat, with her sail dropped and her nose just touching the edge of the float, was quite hidden by this shadow of the island, which was all the darker in contrast with the brilliant moonlight lying on the water farther out. "I'll carry the kedge to the float," whispered Polly, "and then we'll pay out the line till the _Coquette_ floats about over the spot where you think the thing you hit lies." "Let's get my canoe out of the way, too," urged Wyn. "Oh! I hope the boys will not wake up." "What's that light up there?" exclaimed Polly, suddenly. "That's the spark of their campfire. It's in the rocks, so no harm can come from it; they don't trouble to cover it when they go to bed." "Now, Wyn--push the boat off." They worked the catboat from the float for several yards. "Wait," whispered Wyn. "Let's try here." "Are you going to dive?" "Yes. It will make some splash; but I don't believe I can reach the bottom of the lake otherwise, it is so deep here." "Careful!" cautioned Polly. "You may hurt yourself on whatever is down there." "I'll look out," returned Wyn, again filling her ears with cotton. She slipped off the skirt of her bathing suit, too, so as to have more freedom. Then she poised herself for a moment on the decked-over part of the sailboat--a slim, lithe figure in the semi-darkness--and gradually bent over with her arms outstretched to part the water. As she dived forward she thought she heard a quick exclamation from Polly; but Wyn believed it to be an encouraging cry. At least, she gave it no attention as she clove the water and went down, down, down into the depths of the lake. She opened her eyes, but, of course, saw nothing but a great, shadowy mass below her. Toward this mass she swam eagerly; the lake seemed much deeper than it had by daylight. Struggling against the uplift of the water, she beat her way down into the depths for more than a minute. That was a goodly length of time for the first submersion. And she did not reach the bottom, nor find any object like the thing she had struck against some hours before. It was necessary for her to rise. As she turned over, a luminous spot appeared over her head, and toward this spot she sprang. With aching chest she reached the surface, and sprang breast high out of the water--some yards from the catboat. There was a strong current here. "Polly!" she gasped. "Sh!" hissed her comrade's voice, in warning. Surprised, Wyn obeyed the warning. Causing scarcely a ripple in the water, she paddled to the boat. There she clung to the rail and listened. She could not see Polly. "Dunno where they went to in that cat, Eb," growled a hoarse voice out of the darkness.