What the Seafloor Looked Like

The water was extraordinarily clear.

Mara had dived in a lot of places over the years and she had never seen visibility like this. She could see the seafloor from the surface, which should not have been possible at this depth, and as the Pip descended the details below resolved themselves with a sharpness that made her press her face against the porthole and stare.

The seafloor in the surrounding area was what you would expect: sand and rock and scattered coral, the occasional fish moving in long lazy arcs between formations. Normal deep water habitat, beautiful in the particular way that underwater things are beautiful, which is unlike anything on the surface.

But the patch Sol had seen from above was something else entirely.

It was raised, as Sol had predicted, a plateau of rock sitting perhaps ten metres higher than the surrounding seafloor. And the rock was not ordinary rock. It was too regular. Too flat on top. Too precisely edged at the sides, the drop from the plateau to the surrounding floor almost perfectly vertical in places.

And it was covered in structures.

Not coral. Not rock formations. Structures. Low and rounded, built close together in groups, with what appeared to be pathways between them. Some were intact. Others had partially collapsed, their sides caved in, their interiors open to the water. Whatever material they were made of was dark grey and smooth, different from the pale rock of the plateau they sat on.

Sol made a sound beside her that was not quite a word. Mara understood exactly how he felt.

"Buildings," she said. Her voice came out quieter than she intended.

"Buildings," Sol agreed. His face was completely still in the way it got when he was paying maximum attention to something.

The Pip hung in the water above the plateau, its lights illuminating the structures below. They were spread across the entire top of the raised seafloor, hundreds of them, covering an area larger than their school playing field. At the far end of the plateau, partially obscured by a drift of fine silt that had settled over it, was a structure larger than the rest. Much larger. Its outline was different too, not rounded like the others but angular, with what looked like deliberate carved detail on its outer walls.

"How deep are we?" Sol asked, checking the instruments.

"Twenty-two metres," Mara said. "Well within range."

Sol looked at her. She looked at him.

"We are not supposed to exit the sub without Mum," she said.

"I know," Sol said.

"We should go back and get her," Mara said.

"I know," Sol said. He was still looking at the buildings below. "But Mara. Look at it."

She looked. The structures sat on the seafloor in the clear green water, patient and still and ancient, having been there for what might have been an enormously long time without anyone knowing they existed.

"We document everything from in here," she said. "Every camera angle. Every measurement the instruments can give us. We do not exit the sub. And then we go and get Mum."

"Yes," Sol said immediately, already reaching for the camera controls. "Absolutely yes."