"There would be a sensation on Tahiti," he went on, turning to me, "if you showed the traders that shell! It's worth twenty dollars a ton more than the black-lipped variety, and the books say that it produces a great many more pearls. We'll do a bit of prospecting to-day, mark the best places, and let the men begin diving in the morning." We wandered on for several hours, examining the bottom at each halt and marking the more likely spots with a small buoy, moored to the coral with a few fathoms of line. By mid-afternoon, our work seemed finished--we had found more shell than our men could bring up in all the months ahead of us. Our final halt was close to the reef, and there, in about ten fathoms of water, Ofai went overboard for the last time that day. The coral was light-colored at this place and I could see every motion of the diver beneath us. Suddenly, when he had been about a minute under water, I saw him crouch and disappear in a crevice of the rock, and an instant later a long moving shadow passed beneath the boat. "_E mao_!" exclaimed Fatu. "A shark!" My uncle sprang to the side. I leaned over with the rest, watching with acute suspense to see if the shark would move away. No--he had seen Ofai and was turning back toward the deep crevice in which the diver had taken refuge. Then the shark rose toward us and we saw him clearly--longer than our boat, livid-brown and hideous. An exclamation of horror went up from the men. There seemed nothing we could do. Thirty seconds passed; Ofai had been under water a minute and a half. My uncle had reached the limit of his endurance. He spoke to Fatu sharply: "Your goggles! That knife! The other weight!" The shark had approached the surface again, and as he turned to go down, before any of us could utter a cry of protest Uncle Harry went over the side, plunging downward with all the impetus of the heavy leaden bulb. It was an act of the most reckless courage; for in spite of the stories one reads, men do not attack the great sharks of the South Pacific in their own element.