So there's a lot of back story here that I could give. Simmons' Hyperion universe is massive and wonderful, but I'll give the important things for this clip to have context.

-The Hegira, like Mohammed's journey, was the migration of man off of Earth into space when Earth was destroyed.

-The only creatures that were saved, except humans, were dolphins by the citizens of Maui. The believed there was something very important about them, something in their intelligence would be key.

-The dolphins became the caretakers of the motile isles, living islands that moved through the sea, with long tendrils into the ocean. Little is known about them.

I probably missed something. I'm happy to clarify if needed.

We floated side by side in the dim light. Siri was a spectral figure here, her long hair swirling in a wine-dark nimbus, the pale strips of her body glowing in the blue-green light. The surface seemed impossibly distant. The widening V of the wake and the drift of the scores of tendrils showed that the isle was moving more quickly now, moving mindlessly to other feeding grounds, distant waters. “Where are the …” I began to subvocalize.

“Shhh,” said Siri. She fiddled with the medallion. I could hear them then: the shrieks and trills and whistles and cat purrs and echoing cries. The depths were suddenly filled with strange music.

Jesus,” I said and because Siri had tuned our comthreads to the translator, the word was broadcast as a senseless whistle and toot.

“Hello!” she called and the translated greeting echoed from the transmitter; a high-speed bird’s call sliding into the ultrasonic. “Hello!” she called again.

Minutes passed before the dolphins came to investigate. They rolled past us, surprisingly large, alarmingly large, their skin looking slick and muscled in the uncertain light. A large one swam within a meter of us, turning at the last moment so that the white of his belly curved past us like a wall. I could see the dark eye rotate to follow me as he passed. One stroke of his wide fluke kicked up a turbulence strong enough to convince me of the animal’s power.

“Hello,” called Siri but the swift form faded into distant haze and there was a sudden silence. Siri clicked off the translator. “Do you want to talk to them?" she asked.

“Sure.” I was dubious. More than three centuries of effort had not raised much of a dialogue between man and sea mammal. Mike had once told me that the thought structures of Old Earth’s two groups of orphans were too different, the referents too few. One pre-Hegira expert had written that speaking to a dolphin or porpoise was about as rewarding as speaking to a one-year-old human infant. Both sides usually enjoyed the exchange and there was a simulacrum of conversation, but neither party would come away the more knowledgeable. Siri switched the translator disk back on. “Hello,” I said.

There was a final minute of silence and then our earphones were buzzing while the sea echoed shrill ululations.

distance/ no-fluke/ hello-tone?/ current pulse/ circle me/funny?

“What the hell?” I asked Siri and the translator trilled out my question. Siri was grinning under her osmosis mask.

I tried again. “Hello! Greetings from … uh … the surface. How are you?”

The large male … I assumed it to be a male … curved in toward us like a torpedo. He arch-kicked his way through the water ten times faster than I could have swum even if I had remembered to don flippers that morning. For a second I thought he was going to ram us and I raised my knees and clung tightly to the keelroot. Then he was past us, climbing for air, while Siri and I reeled from his turbulent wake and the high tones of his shout.

no-fluke/ no-feed/ no-swim/ no-play/no-fun.

Siri switched off the translator and floated closer. She lightly grasped my shoulders while I held on to the keelroot with my right hand. Our legs touched as we drifted through the warm water. A school of tiny crimson warriorfish flickered above us while the dark shapes of the dolphins circled farther out.

“Had enough?” she asked. Her hand was flat on my chest.

"One more try,” I said. Siri nodded and twisted the disk to life. The current pushed us together again. She slid her arm around me.

“Why do you herd the islands?” I asked the bottle -nosed shapes circling in the dappled light. “How does it benefit you to stay with the isles?”

sounding now/ old songs/ deep water/ no-Great Voices/ no-Shark/ old songs/ new songs.

Siri’s body lay along the length of me now. Her left arm tightened around me. “Great Voices were the whales,” she whispered. Her hair fanned out in streamers. Her right hand moved down and seemed surprised at what it found.

“Do you miss the Great Voices?” I asked the shadows. There was no response. Siri slid her legs around my hips. The surface was a churning bowl of light forty meters above us.

“What do you miss most of Old Earth’s oceans?” I asked. With my left arm I pulled Siri closer , slid my hand down along the curve of her back to where her buttocks rose to meet my palm, held her tight. To the circling dolphins we must have appeared a single creature. Siri lifted herself against me and we became a single creature.

The translator disk had twisted around so it trailed over Siri’s shoulder. I reached to shut it off but paused as the answer to my question buzzed urgently in our ears.

miss Shark /miss Shark/ miss Shark/ miss Shark/ Shark/ Shark/Shark.

I turned off the disk and shook my head. I did not understand. There was so much I did not understand. I closed my eyes as Siri and I moved gently to the rhythms of the current and ourselves while the dolphins swam nearby and the cadence of their calls took on the sad, slow trilling of an old lament.

Later, during the rebelllion, the Web Protectorate (system-wide government) killed all the dolphins and most of the isles with depth charges when fighting against a rebellion that was attempting to protect the way of life of the people, planet, and dolphins.