I have seen this go on for an hour together; after which the shark has made up his mind to have nothing to say to us, and either swerved away to windward, if there be any breeze at all, or dived so deep that his place could be detected only by a faint touch or flash of white many fathoms down.

The loss of a Spanish galleon in chase, I am persuaded, could hardly cause more bitter regret, or call forth more intemperate expressions of anger and impatience than the failure in hooking a shark is always sure to produce on board a ship at sea.
On the other hand, I suppose the first symptom of an enemy's flag coming down in the fight was never hailed with greater joy than is felt by a ship's crew on the shark turning round to seize the bait.
The preparatory symptoms of this intention are so well known to every one on board, that, the instant they begin to appear, a greedy whisper of delight passes from mouth to mouth amongst the assembled multitude; every eye is lighted up, and such as have not bronzed their cheeks by too long exposure to sun and wind to betray any change of colour may be seen to alter their hue from pale to red, and back to pale again, like the tints on the sides of the dying dolphin.
It is supposed by seamen that the shark must of necessity turn on his back before he can bite anything, and, generally speaking, he certainly does so turn himself before he takes the bait; but this arises from two circumstances--one of them accidental and belonging to the particular occasion, the other arising out of the peculiar conformation and position of his mouth.

When a bait is towed astern of a ship that has any motion through the water at all, it is necessarily brought to the surface, or nearly so.

This, of course, obliges the shark to bite at it from below; and as his mouth is placed under his chin, not over it, he must turn nearly on his back before he can seize the floating piece of meat in which the hook is concealed.

Even if he does not turn completely round, he is forced to slue himself, as it is called, so far as to show some portion of his white belly.