Though only just risen the sun was scorchingly hot. There was not a cloud in the sky, not a ripple on the sea. The Jellyfish was a dozen miles or so south of Buenos Aires when, following Baltasar’s advice, anchor was dropped in a small bay near a shore that rose in two rocky ledges straight from the water.

The boats scattered all over the bay. Each was manned by two divers, who did the diving and the hauling in turns.

The diver in the boat closest inshore seized a big piece of coral that was tied to the diving cord between his legs and made swiftly for the sea-bed.

The water was warm and so transparent that you could count the pebbles on the sea-bed. Closer inshore corals rose up like so many bushes of a petrified submarine garden. Small silver-bodied fish flashed in and out among the bushes.

The diver crouched on the sea-bed, quickly picking shells and putting them into the small bag hooked to his leather belt. His tender, a Gurona Indian, his head and shoulders bent over the gunwale for a better view of the diver, held to his end of the diving cord.

Suddenly he saw the diver leap up, snatch at the cord and give it a sharp tug that nearly pulled the Gurona overboard. The boat rocked. The Indian hurried hand over hand with the cord. Presently he was helping the heavily breathing man into the boat. His pupils were dilated, his dusky face ashen.

“Was it a shark?”

But the diver had not recovered sufficient wind to answer.

What could have scared him so badly? The Gurona bent low to the water surface for a better look. Something was definitely wrong down there. The small fry-like birds spotting a falcon-were speeding to the safety of submarine forest thickets.