"That" was a black, triangular object, moving through the water toward the unconscious Herc, who was treading water easily. The dark object came on at a rapid pace, the ripples parting on each side of it as it cut its way along.
The ensign's reply to Ned's exclamation was a cry of alarm.
"Give way!" he shouted. "We've got to get that man quickly, if at all."
Ned looked his question.
"It's a shark!" shot out the ensign, his face ashy-white and his lips sternly compressed; "these waters swarm with them."
Ned was almost unnerved. The boat was still some feet from Herc, and the triangular fin was now close upon the lad.
Suddenly its steady motion ceased, and it shot forward with a rush.
At the same instant Herc perceived his peril, and gave one harrowing shriek, as he saw the terrible nature of the approaching peril.
He swam desperately toward the boats, his countenance strained and lined with the effort and the horror under which he labored.
"Crack!"