WHEN she woke to find herself on the tiny island, she felt no alarm. Her first concern was for her skin; the smiling male clerk in Bermuda's most fashionable store had warned her that a South Sea lava-lava offered very little protection against the white sun. But she wasn't badly burned at all.

The sun had dropped from its position overhead when she had fallen asleep. That had been three hours or so earlier. While she slept, the tide came in and covered most of the peninsula. She'd seen it stretching away from the rest of the shore like a finger pointing out to sea. Its highest point was at the fingertip, where it formed a little hill, and she'd walked out on the peninsula to sit there and be alone for a while.

Everything was very much like the tourist brochures had promised: Bask in the Warmth of a Tropical Sun, Listen to the Whisper of the Surf and Feel the Caress of the Breeze Stealing over You ... She rose and stretched. Her skin felt taut where the sun had gotten at it. The sea wasn't as calm as it had been before the tide started coming in. Her hill on the peninsula was now an island some twenty feet square, and the rest of the slender white strip was under water which she estimated was five or six feet deep, right behind her.

She smiled. It meant she would have to swim back to the beach, and while the distance was no more than two hundred and fifty yards, her lava-lava was considerably—say, two hundred and forty-eight and a half—less. If a man came by on the beach when she happened to be coming out of the water, or before she'd had a chance to dry, well....

Probably the clerk had been thinking something like that when he spoke to her. She remembered her sense of annoyance when she'd felt herself blushing for no good reason. Hell, she thought, I wish I were the man who came by when I climbed out of the water. That made her think of Tom and she smiled again, trying to imagine how it would be if Tom were the man.

She stuck a toe into the water. It felt cool.

Then she saw the gray belly of a shark at it turned over very easily, swimming in the water between her and the beach.

Her eyes teared and a wave of nausea swept through her. She had never before known so profound a fear. This was fear that came up slowly, and it remained, undiminished, for moment after moment. Her muscles tightened and she opened her mouth and sucked in a long breath. Then her fists relaxed and she sank to the ground, suddenly so limp that her legs gave under her weight. But her eyes were fixed on the place in the water where she had last seen the shark, and she saw it come back.

The tip of its dorsal fin was a bare six inches above the cleaved surface of the water. It swam with an effortlessness that made it look as if it were being towed. Neither fins nor tail moved as it floated slowly past, a huge gray and darker gray-brown body in the very blue sea.

SHE lay on her back. A wave broke across the tiny island and the sun made a rainbow in the spray. The shark would leave, she knew. It was unusual for one to have come so near shore at all. The notice at the hotel warned guests not to go swimming in strange or unguarded waters. The shark would go away and then she would quickly swim back to shore. She sat up and looked for the shark.

She had almost decided it was gone when she saw the long shadow sliding across the white sand under water, and the shark reappeared.

The spray caught her again, less delicately this time. When it hit her a third time, she suddenly realized that the island had grown smaller by almost a third, The tide was still coming in. In a little while the whole island would be under water. The shark was swimming more swiftly now. She could see its powerful tail flick as it went by. It was swimming in a circle, and she understood why. The peninsula was sloped, like a bridge that sagged in the middle, and the beach was concave at that point. Now that it was under water, it formed a basin. The shark had entered the basin and was swimming around in it. When the little island would be entirely under water, the basin would cease to exist.

She stood on the hot sand, oblivious to the breeze, shivering when the spray hit her. Both hands were touching her throat, and her eyes kept moving from the water to the horizons of the shore. There was no one in sight.

"Tom'll miss me," she said out loud. She turned toward where she knew the hotel was, perhaps a mile away, but it was out of sight. "He'll comeback to the hotel and ask for me. The sun's down too far for David to continue painting, and Tom'll come back. He'll miss me and he'll come looking..."

Suddenly she screamed. Her fingers recoiled from the feel of the cords in her neck, and she was frightened by the sound she'd heard in her voice.

It would be bad for the hotel. "She came here to be married to a Mr. Thomas Forman," a lady under the green awnings on the terrace was saying, "and on this day—three days before her wedding, poor girl—she put on one of those little what-do-you-call-its and went out swimming. Well, when this Mr. Forman came back to the hotel with his painter friend—a Mr. Stephenson who's a resident here; that house up at the point, if you've seen it—well, he just heard—the first few words and collapsed. Like a sack of—"

"Tom!" she screamed. "Tom! Tom!"

She wondered whether her screaming had brought the shark so close to the surface. Could fish hear sounds from outside the water? It seemed odd to her that she should be crying. She turned slowly and saw how much smaller the island had become. If fish couldn't hear, why did fishermen insist that loud talking frightened them away? She wondered why she was crying.

It was a lovely day. Where the beach ended, the tall grass began, and beyond it lay a grove of fruit trees with a musical name she couldn't remember. The sky was blue enough to be a reflection of the water, and the afternoon sun had gentled. Just like the advertisements said ... except that in the water, twenty feet away—

"Tom!"

He'd come then, as she had known he would. He saw her and came running down the beach with David. He had come back and missed her and come looking for her.

"Tom, I'm marooned! There's a shark here!" she called, rising to her toes. Tom and David both waved to her. Then Tom stopped to peel off his white duck trousers and stood in his swimming trunks. "Tom!" she screamed, and her voice broke.

Tom cupped his hands and shouted through them. The words floated out to her, distorted and hardly audible. "Ohhh-kayy, Linn-da!"

"Shark!" she screamed.

They both waved and Tom went in up to his ankles.

"Shark!"

He was running to meet an oncoming low roller.

Suddenly she swept an arm down and tore the lava-lava from her body. Tom saw her and stopped, and the wave broke against his middle and swept on. He stood there for a moment and then turned to David, and then he backed out of the water. He turned to face her again and his hands made the quick slapping motions in midair that he sometimes used to indicate disapproval.

"Shark!" she screamed. She couldn't see him through her tears, but she stiffened her body against the sobs that shook her. She dropped the cloth to her feet. The next wave that hit the island soaked the cloth and made it a small wet ball.

"NOW what the hell does she want to do a thing like that for?" said Tom. "What a damn fool thing to do!"

Stephenson smiled again. "I'm sorry I can't share that reaction to such a lovely nude. Seriously, though, at that distance and with the sun behind her, we can hardly see her—and don't think she doesn't know it. Feeling good, I suppose."

"Listen, Dave, you know more about things like this than I do. About what happens to girls when they get to a place like this. If—"

"Are you kidding?"

"The hell I am! It isn't as if...well—"

"As if what, Tom?" said Stephenson, very quietly. "As if Linda hadn't been one of my models before you met her through me? As if she was flaunting something? Or as if she was what so many people like you stupidly think of all of them?"

"I'm sorry."

"I wonder."

"All right, then wonder."

"Now I'm sorry," said Stephenson, smiling, "My guess is that she wants to stay out there by herself a while longer—maybe until the island disappears. She likes to play games and she knows you'd never go out after her like that. Especially with me around."

"There's a lot of smirking around here," said Tom.

"I'll meet you back at the hotel," said Stephenson.

"Wait. She's putting it on again."

"Before the tide carries it ashore."

"Anyway, I'm glad she tired of this game fast," Tom said as he started to go into the water again. He hadn't taken three steps when Linda tore off the soaked, clinging cloth.

Stephenson laughed. "Can you hear what she's saying?"

"I don't give a damn. What does she think this—Hell, what if someone from the hotel saw this? My whole damn family's coming in tomorrow, and if a breath of this—"

"What your family needs is a breath of fresh air!"

"Like this, huh?"

"Exactly. Couldn't be better. You stink."

"Go die," said Tom. "That's my girl and I'm going out there to get her." He walked down the beach into the water again. As he went in to his knees, he watched the nude form on the island. He saw Linda bend, swing an arm, and a rock splashed into the water fofty yards away from her. He stood there undecided for a moment. Then he turned, came back up the beach and put on his trousers. "I'm going back to the hotel," he said.

"Why must you be such a jerk?" said Stephenson.

"Because I'm a jerk. Jerk meets girl, jerk loses girl."

"The island won't last much longer. Is it so terrible that she wants to wait? Look at her gathering rocks. She must think you're still coming after her."

"She's wrong," said Tom. "Coming? Or does the spectacle—"

"Oh, shut up."

"You can wait, you know," said Tom. "Sure, I'll tell her."

As he cupped his hands in front of his mouth, Stephenson took him by the shoulder and pulled one of his arms down roughly. Tom spun around, a fist coming up. Stephenson caught the hand halfway up, but he was looking past Torn to the island.

"Tom!" he cried. "Look what she's doing!" He grabbed Tom's other hand and turned him around to face the island. "She's got all those rocks in her lava-lava. She's going to throw it away!"

The girl had evidently made a bundle of the strip of wet cloth and she was swinging it around her like a hammer thrower. She lost her balance and fell, and the rocks tumbled out of the cloth. On all fours she gathered them again.

"She's gone crazy," Tom said in a low voice.

The two men stood there, neither moving, as if finally both were prepared to let the scene come to what now seemed its inexorable end. They watched her swing the weighted cloth again. When she let it go, a soft, strange sound of hurt escaped through Tom's tight lips. The cloth sailed towards shore, scarcely five feet over the Water. It hit, bounced once and sank.

"All right, Tom—Tom! Look!"

From out of the quiet water where the cloth had vanished, a gray form rose in a lightning slash of movement. The water was cut as if by a large black triangular blade, then it was quiet again.

SHE sank to the ground again, and for the first time in a quarter of an hour she stopped crying. She watched the figures of the two men disappear as they ran swiftly down the beach. She couldn't think of anything...then suddenly she felt warmth returning to her body and the blood hammering in her temples. It hardly seemed to her that it was her own voice laughing, as she began to dig...

When the motor launch came roaring along parallel to the shore, she saw Tom and David standing at the prow with two other men who held rifles. She knew they wouldn't see her until they were very close, because she was lying flat in a shallow pit and her body was covered with mud she had made of the sand. The pit was three feet long and half as wide, and it took up three-fourths of the island.

Thirty yards away they saw her and someone held up a blanket.

"Turn around! Everybody turn around!" she shrieked. "I'll stay here until dark if you don't!"

She never understood why Tom and David almost fell apart laughing at that. After all, it wasn't as if...