But reflection showed him a less hazardous way of making an effort to reach the boat.  The sharks’ fins described a semicircle only, as had been the case of his single attendant during the night, and he thought that the shealness of the water prevented their going further than they did, in a south-easterly direction, which was that of the boat.  He well knew that a shark required sufficient water to sink beneath its prey, ere it made its swoop, and that it uniformly turned on its back, and struck upward whenever it gave one of its voracious bites.  This was owing to the greater length of its upper than of its lower jaw, and Mulford had heard it was a physical necessity of its formation.  Right or wrong, he determined to act on this theory, and began at once to wade along the part of the reef that his enemies seemed unwilling to approach.

Had our young mate a weapon of any sort larger than his knife, he would have felt greater confidence in his success.  As it was, however, he drew that knife, and was prepared to sell his life dearly should a foe assail him.  No sooner was his step heard in the water, than the whole group of sharks were set in violent motion, glancing past, and frequently quite near him, as if aware their intended prey was about to escape.  Had the water deepened much, Harry would have returned at once, for a conflict with such numbers would have been hopeless; but it did not; on the contrary, it shoaled again, after a very short distance, at which it had been waist-deep; and Mulford found himself wading over a long, broad surface of rock, and that directly toward the boat, through water that seldom rose above his knees, and which, occasionally, scarce covered his feet.  There was no absolutely naked rock near him, but there seemed to be acres of that which might be almost said to be awash.  Amid the greedy throng that endeavoured to accompany him, the mate even fancied he recognised the enormous fins of his old companion, who sailed to and fro in the crowd in a stately manner, as if merely a curious looker-on of his own movements.  It was the smaller, and probably the younger sharks, that betrayed the greatest hardihood and voracity.  One or two of these made fierce swoops toward Harry, as if bent on having him at every hazard; but they invariably glided off when they found their customary mode of attack resisted by the shoalness of the water.

Our young mate got ahead but slowly, being obliged to pay a cautious attention to the movements of his escort.  Sometimes he was compelled to wade up to his arms in order to cross narrow places, that he might get on portions of the rock that were nearly bare; and once he was actually compelled to swim eight or ten yards.  Nevertheless, he did get on, and after an hour of this sort of work, he found himself within a hundred yards of the boat, which lay grounded near a low piece of naked rock, but separated from it by a channel of deep water, into which all the sharks rushed in a body, as if expressly to cut off