He started the motor, and with the screw reversed put on full speed. But, though the water foamed and bubbled at the stern, the boat remained immovable.

“No go,” declared Jerry. He tried again and again, but without result.

“Somebody’s got to go overboard,” he announced.

“You mean to lighten ship?” asked Andy, and he seemed a bit apprehensive.

“Not yet,” answered the tall lad, with a smile. “I mean someone will have to dive over and see what sort of a thing we’re stuck on. Then we can tell what to do.”

“I’ll go,” volunteered Ned, who was perhaps the best swimmer of the boys. “I wonder if it’s cold?” and he thrust his hand over the gunwale of the boat into the water.

“Is it?” asked Bob.

“Not very. Well, might as well plunge in at once and have it over with.” Ned donned his bathing suit in the cabin, and, a little later, plunged over the side. He dived deeply, and swam under the Scud. Up he came panting for breath, for he was below the surface for some time.

“Well?” asked Jerry, as his chum clung to the rail.