Hour after hour passed. The men took turns at paddling, since there was not a breath of wind. The shark still kept doggedly in company. As the canoe drew farther and farther away from the entrance to the Mohoro River the miasmic mists gradually dispersed, until the three officers found themselves under a bright starlit sky, and on the placid surface of the lagoon there seemed one blaze of reflected brilliance. "It looks as if we are nearing the northern limit of the lagoon," remarked Denbigh. "We'd better keep a sharp look-out for a passage through the reef." "What if we don't find one?" asked Armstrong. "The last gap of any size we passed quite three miles astern." "There's an opening of sorts," announced O'Hara, pointing to a dark patch in the otherwise unbroken line of surf. "My word! I believe there's a spanking breeze outside." "Steady there!" cautioned Denbigh, as the frail craft approached the opening, through which long undulations sullenly rolled in from the vast expanse of the Indian Ocean. "If we get capsized heaven help us. Our old friend has brought up a few more of his pals." The sub was justified in advising caution. Half a dozen sharks were close to the canoe. Emboldened by numbers, they swam around in ever-decreasing circles, until one monster, braver than the rest, rasped his skin along the side of the canoe. As the craft tilted O'Hara aimed a blow at the brute with his paddle. With a swift movement of its powerful tail the shark disappeared, only to rise again and resume its embarrassing attentions. "If those brutes' instinct isn't at fault there'll be a pretty mess-up," thought Denbigh. "They evidently have seen native canoes upset in the channel through the reef before to-day." "Think it's worth while risking it?" asked O'Hara. "No, I don't," replied his chum bluntly. "We must hang on till daybreak, then," said Armstrong. "At dead-low water there may be a trifle less swell." "Yes," assented Denbigh. "We'll land on the lee side of the reef. Gently with her; we don't want to be stove in against a sharp branch of coral." Without accident the landing was accomplished. The adventurers found themselves on a broad part of the reef that was barely three feet above the surface. Seaweed and driftwood had already accumulated, showing that the coral was now only occasionally invaded by the sea. Fifty yards away the surf broke heavily, but fortunately they were out of range of the falling spray. Almost in silence the three chums sat until the sun rose in a grey sky above the horizon. Overhead a few large birds flew seaward--both circumstances presaging a fine day. The tide had now fallen, and, although there were several feet of water in the channel, a detached reef about a hundred yards from the main coral ledge, which had uncovered as the tide fell, completely broke the breakers for some distance on either side of its seaward end.