Part 3 (1/2)

Once the boys were aboard, the seacopter submerged and dived quickly to the ocean floor. Tom and Bud each climbed into a Fat Man suit and went out through the air lock. The suits, shaped like huge steel eggs with a quartz-gla.s.s view plate for the operator seated within, had mechanical arms and legs.

The boys waddled about, the built-in searchlights of their suits piercing the murky gloom. They saw nothing but the deep acc.u.mulation of silt on the ocean bottom, which made the going difficult.

”This is too slow,” Tom called over his sonarphone. ”Let's try the air dome.”

The dome was a huge underwater bubble of air, created by a repelatron device which actually pushed the ocean water away. The air supply inside was kept pure by one of Tom's osmotic air conditioners which made use of the oxygen dissolved in the water.

The air bubble, however, even with its jet-propelled platform, also proved inadequate for the research job. Its caterpillar treads repeatedly bogged down in the silt.

”Maybe the seacopter itself is our best bet,” Bud suggested.

”Worth a try,” Tom urged.

But the _Sea Hound_, too, had a serious drawback. Even with its powerful search beam sweeping the ocean floor as it prowled along, the explorers found their vision too limited.

Finally Tom said, ”Bud, we could skin-dive at this depth.”

”Let's give it a whirl,” Bud urged.

The seacopter surfaced again, while the boys donned flippers, masks, and air lungs. Then they dropped over the side and made their way slowly downward into the gray-green depths, accustoming themselves gradually to the increased pressure.

”A lot more freedom of action,” Tom thought. ”If only we didn't have to communicate by signals!”

There was a sudden _swoosh_ somewhere on his right. A projectile, Tom realized! Turning, his eyes widened in horror as he saw an uprush of bubbles.

Bud's air tank had been hit!

CHAPTER III

INVISIBLE SUB

Without wasting a moment, Tom lunged through the water toward his stricken friend. Bud was floundering and thras.h.i.+ng about weakly. He seemed dazed by the sudden shock of his plight.

”Or maybe the impact of the projectile stunned him!” Tom surmised.

Bud began groping his way upward just as Tom came alongside of him. Tom grabbed him as best he could, hooking onto his belt. At the same time, the young inventor inhaled deeply, yanked out Bud's useless mouthpiece, and inserted his own in its place.

Bud's eyes glowed with grat.i.tude.

”We'll have to get topside fast,” Tom thought, ”even though it means risking the bends.”

He stroked upward and they shot toward the surface. Bud a.s.sisted to some extent, partly revived by the gulp of air.

As they rose, fathom by fathom, their progress seemed to grow maddeningly slower. Tom had to let air bubbles escape constantly from his mouth. As the pressure decreased, due to the lessening depth of the water, the air in his lungs expanded and he was forced to breathe out.

Tom noticed with dismay that Bud was not responding very well, his feeble strokes were jerky and uncoordinated. ”Must've lost pressure too fast when his tank was. .h.i.t,” Tom realized.

The water was growing greener and brighter now as they neared the suns.h.i.+ne. The _Sea Hound_'s shadowy outline loomed just above. With a last desperate burst of strength, Tom lunged upward and they broke water.