“Roger that,” Michaela told her. “We’re flipping on the instruments. We’ll take station ten meters off your stern and match depth.” In her monitors she kept track of the second sub as it passed above, turned into the reef, and nosed close to the bottom so that Varina could begin taking samples with the sub’s extendable arms. Even as she did, the observers in the Pod began chattering. Michaela deleted the distraction, setting her com to react if a request was directed to her.

To Casey, she said, “Point us out toward deepwater. I’m turning on the sonar.”

“Got it. And I’ve got Jaim and Varina’s location on my instruments. They’re nosing into position now.”

Michaela watched as the sub’s orientation shifted, swinging them around to the open water where it shone in a marvelous turquoise that seemed to fade into infinity. Beams of light danced from the waves above, reminding her of the magic of being underwater. The heads-up display reflected sonar hits on tubes and other creatures as tiny blips of yellow on the screen.

“Michaela?” Varina’s voice came through the com, “Try the hydrophones. You’ve got to hear this. You’ll need to use the program to mask the mechanical sound of the subs, but this is amazing.”

“Roger that.” Michaela accessed her implants to turn on the hydrophones, overwhelmed at first by the wealth of sound. Then, from memory, she used the program to remove the hum from the electric motors on the two subs.

“How do you describe that?” Casey asked as she established neutral buoyancy at a depth of five meters, her eyes on the instruments.

“Like that sound you hear when an orchestra is tuning up before playing a symphony.” Michaela made a face. “But not really. There’s so much more range here above and below our hearing. I’m getting readings from four hertz to two hundred and twenty kilohertz. It’s the tremolo, the harmony, almost a rhythm. Then there’s the bumping bass. Deep thrumming. A chorus of sound. Like nothing I’ve ever heard. Even more complex than the chime we heard outside Port Authority.”

“You ask me,” Casey told her, “the whole ocean is singing.”

For long moments, they just sat there listening. Fascinated and not a little awed as tubes darted past the transparency and occasionally hit it hard enough to give off soft thumps.

Michaela got a ping on sonar, watching the Doppler that marked the creature’s approach from off to the left. Given the signal return, it measured close to four meters, but seeing it appear out of the blue, first as a shadow, only to solidify into a four-flippered . . . No, that was wrong. These were like four underwater wings that shot the organism forward, then, at sight of the sub, flashed to spin the creature into an impossible right-angled flight where it disappeared into the distance.