As he placed the last sponge in the basket he turned to signal to his chum to ascend, but Walter was already gone, his figure, grotesque in the diving suit, was already well up from the bottom and shooting up with astonishing swiftness. At the same moment Charley became aware of a strange sickening sensation. He was choking and gasping for breath. Before he could realize what had happened the frightful sensation had passed and he was able to breathe fully and freely, and he felt himself being pulled swiftly to the surface.

In a moment he was hoisted above the surface, hauled aboard the boat and his helmet removed. The captain, white-faced and shaken was leaning against the mast his revolver in his hand. Chris, ashen-hued, and a sailor, was still pumping faintly. Close beside the air pump lay Manuel in apparent unconsciousness.

"What's happened?" Charley cried.

"Manuel keeled over in a fit or something," said the captain, brokenly. "I thought you would both be dead before we could get you to the surface. It seemed ages before I could get Chris to the pump and the fellows to hauling you up. They seemed to move mighty slow 'till I threatened to shoot. They maybe didn't understand what I said but the sight of the gun made 'em more lively," he concluded, grimly.

Charley walked over to the prostrate Greek and stood gazing down at his upturned face.

"He has no business to faint when he's working the air pump," he said savagely. "I guess I'll kick him a good hard one in the face for punishment."

The manly lad had no such intention of carrying out such a brutal threat but he wanted to test whether the treacherous Greek was, as he suspected, really shamming.

The prostrate man's features twitched, he sighed heavily and rolled over on his side, Charley's suspicions were confirmed.

"Captain," said the lad distinctly, "if anything happens to Walter and I when we are below the surface, I want you to shoot this man without the slightest hesitation. He is the only one who can understand your orders and he must be made responsible for our safety."