The melody lingered in Amara's mind as she returned to the surface, a phantom echo that refused to be silenced. It was a puzzle that demanded her attention, and she knew exactly where to start looking for answers.

In the corner of the research platform's archive room lay a collection of dusty files labeled "Project Lumina." These were records of the forbidden research, a series of experiments with bioluminescent algae that promised a revolution in sustainable energy.

Amara donned a pair of white gloves and began to sift through the papers. The project had been ambitious, harnessing the natural light of algae to create a living power source. But something had gone wrong. The notes grew increasingly frantic, the handwriting shaky. The last entry was a single, scribbled sentence: "We've awakened something."

The project had been shut down overnight, the researchers reassigned, and the algae forgotten. But the reef remembered. The silence of the coral was a testament to that.

As Amara dug deeper, she uncovered a hidden folder, tucked away as if someone had hoped it would never be found. Inside were photographs of vibrant coral, glowing with an unnatural light, and transcripts of interviews with the researchers, their voices tinged with fear.

They spoke of the algae's unexpected growth, of how it began to spread, to change. They whispered of the song, a melody that had begun as a whisper in the lab, growing louder as the algae thrived.

The final piece of evidence was a grainy video, showing a tank of water illuminated by the eerie glow of the algae. And there, in the background, was the song, a haunting tune that seemed to come from the algae itself.

Amara sat back, the pieces of the puzzle falling into place. The forbidden research had unlocked something within the algae, something that had silenced the reef. And now, it was up to her to find out why.