He turned the wire by which the submarine ear hung from the rail. The chirpings and squealings and squeakings changed volume as the microphone turned. But the new sound, of something rushing at high speed through the water--that did not change. Terry rotated the mike through a full circle. The fish noises dwindled to almost nothing, and then increased again. The volume of the steady hum changed with them. But the rushing sound remained steady. Rather, it grew in loudness, as if approaching. But the directional microphone didn't register any difference, whether it received sound from the north, east, south, or west. It was a booming sound. It was a rushing sound. It was the sound of an object moving at terrific speed through the water. There was no engine noise, but something thrust furiously through the sea, and the sound grew louder and louder. "It's not coming from any compass course," said Terry shortly. "How deep is the water here?" "We're just over the edge of the Luzon Deep," said Davis. "Four thousand fathoms. Five. Maybe six." "Then it can only be coming from one direction," said Terry. "It's coming from below. And it's coming up." For three heartbeats Davis stood perfectly still. Then he said, with extreme grimness, "Since you mention it, that would be where it's coming from." He turned away and shouted a few orders. The crewmen scurried swiftly. The yacht's head fell away from the wind. Terry listened again to the rushing sound. There seemed to be regular throbbings in it, but still no engine noise. It was a steady drone. "Bazooka shells ought to discourage anything," Davis said in an icy voice. "If it attacks, let go at it. But try to use the gun-cameras first." The _Esperance_ rolled and wallowed. Her bows lifted and fell. Her sails were black against the starry sky overhead. Two of the crew-cuts settled themselves at the starboard rail. They had long tubes in their hands, tubes whose details could not be seen. The wind hummed and thuttered in the rigging. Reef-points pattered. Near the port rail the recorder poured out the amplified sounds its microphone picked up from the sea. The sound of the coming thing became louder than all the other noises combined. It was literally a booming noise. The water started to bubble furiously as it parted to let something rise to the surface from unthinkable depths. Doug put two magazine-rifles beside Terry and Deirdre, then he moved away. Deirdre had a clumsy object in her hands. It had a rifle-stock and a trigger. What should have been the barrel was huge--six inches or more in diameter--but very short. That was the flashbulb reflector. The actual camera was small and on top, like a sight. "We'll aim these at anything we see," said Deirdre composedly, "and pull the trigger. Then we'll pick up the real rifles and see if we must shoot. Is that all right?"