flopped into the boat, shaking with
laughter, surfacing and diving.

"What was so funny down there?" Zimby asked.

When Tom told him about the dolphins, he too burst into laughter. The
porpoises rose into view and convoyed the launch all the way back to the
island.

The boys were so jubilant over the performance of the new hydrolung gear
that Tom decided to press his search for the Brungarian sea-prowlers
immediately. Soon after lunch they took off in the _Sea Hound_ and
headed for the South Atlantic. Hank Sterling, Chow Winkler, and two
crewmen accompanied the boys.

Dazzling afternoon sunshine sparkled over the sea when they reached the
missile search area. Tom immediately contacted Art Wiltessa and the
task-force ships. They had no new developments to report.

The young inventor gave orders to submerge. As soon as the seacopter
touched bottom, Tom and Bud swam out through the air lock with their
hydrolungs.

They probed about for half an hour, ranging farther and farther from the
_Sea Hound_. Then Tom felt a touch on his arm. He turned and saw Bud
pointing off excitedly to the right.

A strange submarine was moving slowly toward them!

CHAPTER VIII

DATE TROUBLE

The boys exchanged looks of fear through their face masks as the
knifelike hull and conning tower of the submarine loomed gray and
ghostly.

Was the sub Brungarian? And what was it up to? Were the two young skin
divers about to be run down or kidnaped?

_Or was its crew friendly?_

"Better not chance it," Tom decided fast. He caught Bud's eye again and
motioned upward with a jerk of his thumb. "Topside, pal!"

"Roger!" Bud's lips shaped the word silently behind his face mask.

In a twinkling both boys flicked their density controls and zoomed
upward. The sub at once seemed to betray a hostile intent. It blew its
tanks and planed upward in pursuit. But Tom and Bud easily pulled away.
Their density units worked like magic, shooting them straight toward
the surface.

"Wow!" Bud shoved back his face mask as they broke water. "That baby was
after us and no mistake!"

Tom nodded, treading water. "Let's not stick around here, either! We'll
soon have company again if we do!"

Bud did not argue. "Where to, skipper?"

In the fresh salt air, with the sunshine sparkling on the waves, it was
hard to believe that an enemy submarine was hot on their trail. But both
youths realized their peril was growing by the moment.

"Back toward the