The creatures under the sea had not. They'd send up giant squids to do battle with men, as men once sent elephants against the Macedonian army. It was naïve. But the generals, the tacticians, the strategists of the Deep did not remain wedded to the one weapon. Already, they saw that beasts could be fought by men. So their instruments of battle changed. Doubtless, orders were given, and five miles under the sea something--something men could not have duplicated--began the transformation of seawater into gas, in quantities past imagining. Tiny, tiny bubbles were produced by some unguessable engine, and rose toward the surface, in a steady stream. At the bottom they were under a pressure of tons to the square inch. But the pressure lessened as they rose, and as they rose they swelled. A bubble which was pinhead-size at the sea-bed grew to be the size of a basketball a half-mile up, and would have been the size of a house a mile up, except that then it separated into smaller ones. They rose and rose and expanded and separated. Five miles up from their origin, at little more than atmospheric pressure, they made a rising column of insubstantiality. At the surface they became foam. But under the foam there was more foam, and under that still more. A ship sailing from normal ocean water into such airy stuff would drop like a stone into the miles-long cone of semi-nothingness. Nothing solid could float there. Nothing substantial could rest its weight upon such rushing thistledown. And the first of the bubble-weapons appeared at the surface in the form of a patch of foam. Its source--and hence the place of its appearance--could be moved. It could be shifted under any ship, though there would be a time-interval, always, before the foam at the surface was exactly above the gas-generating engine below. It could be moved to anticipate the movements of a ship. But there was always that time-lag. The _Esperance_ headed back toward the heap of monsters at the break in the reef. Other giant squids emerged and joined the pack. A plane came over and bombed it. The _Esperance_ turned away. The mine layer from Manila appeared at the horizon. The flattop made a sudden violent turn, and more foam appeared upon the water. It curled and writhed and piled up to be ten--twenty--thirty yards in height. The flattop fired a shell into it. There was a gigantic flash and flame, and for an instant there was no foam, but only peculiarly pock-marked ocean surface, instantly covered by more foam which piled up as before. "Gas," said Terry grimly. "Hydrogen. You guessed right, Deirdre!" Now the flattop shot off plane after plane, as if they were projectiles. They swung in the air and flew low to drop bombs in the now wabbling, moving, sweeping patch of white stuff. It was a huge discoloration of the ocean surface. It was almost in diameter as the flattop's length. Now the carrier dodged it warily.