Rick consulted his wrist depth gauge, holding it close to his face plate. They were at bottom at ninety feet, and the clean sand dropped away at an angle of about thirty degrees. The boys planed downward, a few feet above the sand until Rick's gauge read 120 feet. This was the limit of their dive. Going deeper would mean stopping for decompression on the way up.
He recalled that the waves came into the beach from a slightly northerly direction and motioned to Scotty that they should turn north. Scotty moved out to the limit of visibility, and they swam on a compass heading of north, watching for any sign of a wreck. Now and then a coral shelf extended out from the reef, but they saw nothing that could have been a wreck. Once they swam over a patch of marine growth perhaps twenty feet long and ten wide, and a huge eagle ray lifted from it and glided off like a weird futuristic airplane.
It was quiet, except for the regular chuckle of their exhausts, and the light was subdued and even. It was a world without shadows. Still, Rick thought, there was plenty of light for photography. Next time he would bring his camera.
The watch showed him that over half their allotted time was gone, and he hooted once to Scotty, then reversed course, heading back toward their floats.
They approached the patch where they had seen the ray and Rick paused suddenly. There was an odd shape on the sand near the patch. He flippered over to it and examined it. Scotty joined him. It looked like an oversized mushroom protruding from the sand at an angle.
Rick unsheathed his knife and poked at it. The sharp tip penetrated for a fraction of an inch, then stopped. It was either rock or metal, and judging from the shape, it was unlikely that it was rock. He put his knife under it and pried, and the thing moved in the sand.
Both boys went to work on it, scooping the sand from around it. In a moment they had it clear. It was something like a dumbbell, covered with marine growth where it had been above the sand, but fairly smooth under it.
Rick took his belt slate and scribbled, "Metal."
Scotty nodded. Then both of them turned to look at the patch of marine life.
A distant throb, as though of a boat, caught their attention. They looked up, but the surface was invisible.