Terry reeled back a few feet of the tape which contained the whacking sounds. He re-played them, listening critically as before. Tony had returned to the deck. The whackings, as heard underwater, were not merely impacts. There was a resonance to them. Almost a hum. Rather grimly, Terry substituted this tape-reel with the recording he'd made the night before. He started the instrument and found the exact spot where the object from the depths had fallen back into the sea. He stopped the recorder right there. He hauled up the submarine ear and plugged in the horn to the audio-amplifier, as yet untested, which should multiply the volume of sound from the tape. Then he put the horn overside. He switched on the recorder again. The tape-reel began to spin. The sound went out underwater from the horn. Underwater it was much louder than when it had been received by the _Esperance's_ microphone. Here it was confined by the surface above and the harbor-bottom beneath. It must have been the equivalent of a loud shout in a closed room--only worse. The fish in the harbor of Barca went mad. All the harbor-surface turned to spray. Creatures of all sizes leaped crazily above the surface, their fins flapping, only to leap again, more frantically still, when they fell back. A totally unsuspected school of very small flying fish flashed upward in such frenzied haste that some tried to climb too steeply and fell back and instantly flung themselves into the air again. Terry turned off the playing recorder. The disorder at the top of the water ceased immediately. But he heard shrill outcries. Children had been wading at the edge of the shore. They stampeded for solid ground, shrieking. Where their feet and legs had been underwater they felt as if a million pins and needles had pricked them. Something flapped heavily on the _Esperance's_ deck. Tony went to see. It was a three-pound fish which had leaped clear of the water and over the yacht's rail to the deck. Tony threw it back into the water. "I guess there's not much doubt," he said painfully. "Of what?" demanded Terry. "Of what ... I had guessed," said Tony. "And what did you guess?" Tony hesitated. "I guess," he said unhappily, "that I'd better not say." He watched with a startled, uneasy expression on his face as Tony put the apparatus away. Time passed. Davis and Deirdre had been ashore over an hour. Then Terry saw the small boat leave the shore and approach. It came deftly alongside, the two passengers climbed up to the deck, and all four crew-cuts hauled the boat back inboard and lashed it fast. "Our dredge isn't ready yet," said Davis. "It looks good, but there'll be a delay of a few days." Deirdre examined Terry's expression. "Something's happened. What?" Terry told her. Davis listened. Tony added what he'd seen, including the fish that had leaped high enough out of the water to land on the _Esperance's_ deck.