Scotty checked his spear gun and motioned for Rick to lead. Rick pushed his camera in front of him and made his fins move rapidly. There might be some outward sign when the ball sounded, something that would tell them a little about its mechanism or purpose.
As the cave came in view he coasted, looking upward. The murky layer prevented his seeing very far, but there was no one in sight. He let inertia carry him toward the cave, then swung upright in the water as he saw that the octopus had moved a little distance from the cave mouth.
Instinctively Rick knew that something was wrong, but it was too late to get out of harm's way.
A frogman emerged from the cave, spring-type spear gun pointed directly toward them. The frogman held the brass instrument in his free hand.
Even as Rick hooted a warning, the frogman fired!
His spear lanced through the water directly at Scotty!
CHAPTER XVII
Trapped in Twenty Fathoms
Scotty writhed to one side, and the fact that the frogman had fired from too great a distance gave him time to dodge. The spear went by, and Scotty lifted his own gun to return the shot.