I stood watching those two sharks as they swam lazily to and fro between me and the fast receding wreckage.  It really looked as though they were aware of my presence, had divined my purpose, and were determined to frustrate it.  For what seemed at least half-an-hour, but was probably not more than ten minutes, the voracious fish tacked this way and that, approaching me a little nearer every tack, until at length they were so close that I could have leapt upon the back of the nearer one, so close that I could distinctly see their entire bulk; and the sight turned my blood cold, for they were veritable monsters, one of them being fully twenty feet long from snout to the tip of the unevenly fluked tail, while the other was perhaps three feet shorter.  And there was now no room to doubt that they were fully aware of my existence, for every time that they passed me their great goggle eyes glared at me hungrily with an expression which seemed to say--"All right, my boy; you may hold on there as long as you like: but we will wait for you, and get you at last."