A savage-looking creature slithered toward him. A barracuda, by God, a big one, only two or three feet shorter than Shayne himself. Shayne waved his big fist in the fish’s bared teeth. It flickered away.

The waving blob of a jellyfish was drifting below him, or perhaps above him, depending on whether he was swimming up or down. Shayne veered away, into a small disciplined army of spade fish. They scattered past.

The charts showed the reef at this point to be eighty feet down. But it shoaled sharply to the east, and Shayne hoped he would strike a trench which would carry him down to a hundred feet or beyond. He had always known, he realized, that by passing the invisible hundred-foot barrier he would break into a new and far more interesting dimension.

The high, steady singing of the regulator set off a peculiar overlapping echo in his head. Without understanding the reason for it, he found it far from unpleasant. He had been working too hard, drinking too much, sleeping too little. Once he was down to a hundred feet, he felt sure, the echo would disappear and his vision would sharpen. The truth was, something odd was beginning to happen to the light. Instead of staying a constant shade, somewhere between green and gold, it shifted to violet and was steadily darkening. The color now was like a spreading stain in the water.

Another large, supple fish swam at him through the violet murk. But it wasn’t a fish at all, Shayne noted with surprise. It was a mermaid wearing a white bikini.

And then as it approached closer, the creature’s tail turned into flippers. It was only a woman after all, Shayne was disappointed to see. She had long blonde hair, which was waving like seaweed. Her features were concealed by a glinting face plate. He wondered vaguely how she managed to get along down here without air. He checked his depth regulator again, and now, instead of two needles, there were none at all. The figures on the dial had swum away.