The male spread his eight arms, raised his two long tentacles, and his green binocular eyes fixed on the barracuda. Confusing patterns of light and shade pulsed across his hide. Look at me. I am large and fierce, lean kill you.

The metal barracuda hung in the water, apparently mesmerized by the pattern, just as a predator should have been if it had been real.

Slowly, cautiously, the male drifted toward the barracuda, coming to within a mantle length, gaze fixed on the fish.

At the last moment the barracuda turned, sluggishly, and started to slide away through the water.

But it was too late for that.

The male lunged. His two long tentacles whipped out — too fast even for Sheena to see — and their clublike pads of suckers pounded against the barracuda hide, sticking there.

The barracuda surged forward. It was unable to escape. The male pulled himself toward the barracuda and wrapped his eight strong arms around its body, his body pattern changing to an exultant uniform darkening, careless now of detection.

But when the male tried to jet backward, hauling at the prey, the barracuda was too massive and strong.

The male broke the standoff by rocketing forward until his body slammed into the barracuda’s metal hide — he seemed shocked by the hardness of the “flesh” — and he wrapped his two long, powerful tentacles around the slim gray body.

Then he opened his mouth and stabbed at the hull with his beak. The hull broke through easily, Sheena saw; evidently it was designed for this. The male injected poison to stun his victim, and then dug deeper into the hide to extract the warm meat beneath. And meat there was, what looked like fish fragments to Sheena, booty planted there by Dan.

The squid descended, chattering their ancient songs, diving through the cloud of rich, cold meat, lashing their tentacles around the stricken prey. Sheena joined in, her hide flashing in triumph, cool water surging through her mantle, relishing the primordial power of this kill despite its artifice.

That was when it happened.

Maura Della:

“Ms. Della, welcome to Oceanlab,” Dan Ystebo said.

As she clambered stiffly down through the airlock into the habitat, the smell of air freshener overwhelmed Maura. The two men here, biologist Dan Ystebo and a professional diver, watched

her sheepishly.

She sniffed. “Woodland fragrance. Correct?”

The diver laughed. He was a burly fifty-year-old, but the dense air mixture here, hydreliox, turned his voice into a Donald Duck squeak. “Better than the alternative, Ms. Della.”

Maura found a seat between the two men before a bank of controls. The seat was just a canvas frame, much repaired with duct tape. The working area of this hab was a small, cramped sphere, its walls encrusted with equipment. It featured two small, tough-looking windows, and its switches and dials were shiny and worn with use. The lights were dim, the instruments and screens glowing. A sonar beacon pinged softly, like a pulse.

The sense of confinement, the feel of the weight of water above her head, was overwhelming.

Dan Ystebo was fat, breathy, intense, thirtyish, with Coke-bottle glasses and a mop of unlikely red hair, a typical geek scientist type. Igor to Malenfant’s Doctor Frankenstein, she thought. His face was underlit by the orange glow of his instrument panel. “So,” he said awkwardly. “What do you think?”

“I think it feels like one of those old Soviet-era space stations. The Mir, maybe.”

“That’s not so far off,” Dan said, evidently nervous, talking too fast. “This is an old navy installation. Built in the 1960s, nearly fifty years ago. It used to be in deep water out by Puerto Rico, but when a hab diver got himself killed the navy abandoned it and towed it here, to Key Largo.”

“Another Cold War relic,” she said. “Just like NASA.”

Dan smiled. “Swords into ploughshares, ma’am.”

She leaned forward, peering into the windows. Sunlight shafted through dusty gray water, but she saw no signs of life, not a fish or frond of seaweed. “So where is she?”

Dan pointed to a monitor, a modern softscreen pasted over a scuffed hull section. It showed a school of squid jetting through the water in complex patterns. The image was evidently enhanced; the water had been turned sky blue. “We don’t rely on naked eye so much,” Dan said.

“Which one is Sheena Five?”

Dan touched the softscreen image, picking out one of the squid, and the virtual camera zoomed in.

The streamlined, torpedo-shaped body was a rich burnt orange, mottled black. Winglike fins rippled elegantly alongside

the body.

“Sepioteuthissepioidea” Dan said. “The Caribbean reef squid. About as long as your arm. See her countershading? The light is downwelling, corning from above; she has shaded her mantle — brighter below — to eliminate the effect of shadow, making herself disappear. Squid, all cephalopods in fact, belong to the phylum Mollusca.”

“Molluscs? I thought molluscs had feet.”

“They do.” Dan pointed. “But in the squid the foot has evolved into the funnel, here, leading into the mantle, and the arms and tentacles here. The mantle cavity contains the viscera — the circulatory, excretory, digestive, reproductive systems. But the gills also lie in there; the squid ‘breathes’ by extracting oxygen from the air that passes over the gills. And Sheena can use the water passing through the mantle cavity for jet propulsion; she has big ring muscles that—”

“How do you know that’s her?”

Dan pointed again. “See the swelling between the eyes, around the esophagus?”

“That’s her enhanced brain?”

“A squid’s neural layout isn’t like ours. Sheena has two nerve cords running like rail tracks the length of her body, studded with pairs of ganglia. The forward ganglia pair is expanded into a mass of lobes. We gen-enged Sheena and her grandmothers to—”

“To make a smart squid.”

“Ms. Della, squid are smart anyway. They are molluscs, invertebrates, but they are functionally equivalent to fish. In fact they seem to have evolved — a long time ago, during the Jurassic — in competition with the fish. They have senses based on light, scent, taste, touch, sound — including infrasound — gravity, acceleration, perhaps even an electric sense. See the patterns on Sheena’s hide?”

“Yes.”

“They’re made by chromatophores, sacs of pigment granules surrounded by muscles. The chromatophores are under conscious control; Sheena can open or close them as she chooses. The pigments are black, orange, and yellow. The underlying colors, blues and violets, are created by passive cells we call reflecting Ms. Della, Sheena can control her skin patterns consciously. She can make bands, bars, circles, annuli, dots. She can even animate the display. The mantle skin is like a reverse retina, where neural signals are converted to patches of shade, rather than the other way around.”

“And these patterns are signals?”

“Not just the skin patterns. A given signal seems to be made up of a number of components: the patterns; skin texture — rough or smooth; posture — the attitude of the limbs, head, body, fins; and locomotor components — whether Sheena is resting, jetting, hovering, grabbing, ink jetting. There may be electric or sonic components too; we can’t be sure.”

The diver growled, “Ms. Della, we’ve barely scratched the surface with these animals. Not to mention their deep-water cousins. Until the last few decades all we did was lower nets and see what we could catch. We used to say it was like trying to understand the animals of the land by working with a butterfly net from a balloon in the clouds.”

“And what do they use this marvelous signaling for?” Maura asked.

Dan sighed. “Again we aren’t sure. They don’t hunt cooperatively. They forage alone by night, and shoal by day. The shoaling seems to be to provide protection while they rest. The squid don’t hide on the bottom like octopuses; they shoal over sea grass beds where there are few predators. They have elaborate courtship rituals. And the young seem to learn from the old. They post sentinels. Very effectively, too; though they may have six or seven predator encounters per hour — with yellow jacks and mutton snappers, barracuda and houndfish, coming at them from anywhere — the squid kill rate is very low.