"Some other time," he called back. "We're terrible busy today.
Goodbye."
The German officer gave a sharp command. Several sailors sprang to their feet and blazed away at the hydroplane with their rifles. Bullets flew by on all sides, but none struck home.
Again Jack waved his cap.
"Very bad shooting," he remarked. "Looks like some of my—Hello! That wasn't so bad."
For the lad's cap, which he had been waving in derision at the pursuing foe, was suddenly carried from his hand by a German bullet.
"By Jove!" said Jack, quietly, "I wouldn't have lost that cap——" He gazed at it as it floated in the water.
And at that instant Frank sent the hydroplane soaring into the air with a lurch. Jack glanced down into the water.
"Hold on, Frank!" he cried.
In response to this command, Frank slowed down.
"What's the matter now?" he demanded.