For some moments Captain Jack paid no especial heed to the launch bearing down upon them on the port side. He noted only, at the distance, that the launch contained two men. Presently, however, as the launch came nearer, Captain Benson made a discovery.
"Eph," he gasped, "look over there! Are my eyes going back on me, or is that a Japanese in the bow of the launch?"
"Japanese?" gasped Eph Somers, in turn. "Nothing but!"
Eph made a swift dive for the box that contained the signal flags used in the international marine signaling code. Moving swiftly, young Somers selected the two flags representing "N" and "D." These he strung to the halliard of the short signal mast forward. Nor was he ahead of time, for by this time the launch had described part of a circle, and was coming up alongside.
In the bow of the launch stood the Japanese, smiling, and holding a megaphone in his hand.
"Submarine, a-ho-o-o-oy!" came the hail. "Will you slow down? I have something to say to you."
Up flew the signal flags, fluttering in the breeze. Then Eph snatched up a megaphone, holding the smaller end to his mouth.
"Launch ahoy!" he shouted back. "Just tell your folks that you saw our signal!"
The Japanese read the fluttering flags, then called back:
"N.D.? What does that mean?"