Immediately following the Captain's shouts, a great hulk loomed up right beside the yacht, and a fearful blow to the rear end of the pleasure craft sent her flying diagonally out of her path, across the water. The collision made her nose dip down dangerously while the stern rose up clear of the waves. The group seated forwards slid together, and some were thrown from their chairs, but managed to catch hold of the ropes and rail to prevent being thrown overboard. Polly and Tom, standing, unaware, so near the open gap in the rail, still arm in arm as they had been walking, were thrown violently side-ways and there being nothing at hand to hold to, or to prevent their going over the side, they fell into the dark sea. Feeling as if the earth had dropped from under her, Polly screamed in terror before her voice was choked with water. Tom instinctively held on to her arm, as he had been doing when the impact of a larger vessel came upon the yacht, and he maintained this grip as they both sank. Polly had always dreaded water, because it seemed so unfamiliar to her. After living in the mountains with only narrow roaring streams, or the glacial lakes found in the Rockies, she had never tried to swim in the ocean, but preferred swimming in a pool. Consequently, this sudden dive into the awesome black abyss so frightened her, that she fainted before she could fight or struggle. But Tom Latimer was an expert swimmer, having won several medals while at College for his continued swimming under water. At one time during his first college days, he had saved the lives of some young folks when their canoe capsized a long distance from shore. In this supreme test of ability and presence of mind, with the girl he loved in his arms to save, Tom was as self-possessed as if on deck with Polly. In less time than it takes to tell, both victims of the collision sank until the natural fight between the weight of the water and the force of the air in their lungs, sent them up again to the surface. In that short time, Tom used every muscle and physical power to swim far enough _under_ the water to clear away from the boats which might do them more harm than the water. Fortunately he found the surface free when he rose for breath, and finding no resistance from the unconscious form he held, he managed to change his grip from her arm to a firm hold under the shoulders. In this position he could manage to keep Polly's head above water, and at the same time, could swim backwards, by using his feet as propellers. The only handicap he now had, was his clothing and shoes; these interfered with his free action in swimming so he managed to kick off his dancing pumps. The greatest danger he feared, was the sudden coming of some craft that would compel him to dive again, or might even run them down, unseen in the dark.