He was half-whirled about in the vortex of the thing's passage caused by the alarmed flirt of its tail.

Shark it was, and not crocodile, and not so timidly would it have sheered clear but for the fact that it was fairly full with a recent feed of a huge sea turtle too feeble with age to escape.
Although he could not see it, Jerry sensed that the thing, the instrument of nothingness, lurked about him.

Nor did he see the dorsal fin break surface and approach him from the rear.

From the yacht he heard rifle- shots in quick succession.

From the rear a panic splash came to his ears.