Y/n moves through it alone, as she always does. The water parts around her like silk, her tail catching the dappled light filtering down from the surface. A school of silverfish parts ahead of her, and she pays them no mind. She is watching the shadows between the rocks.

And then she feels it. A change in the water. A pressure, low and heavy, pushing against her from behind. Not a current. Something alive. Something large enough to displace the sea itself.

She turns.

A mershark hangs at the edge of her territory, half-shrouded in the murk. He is enormous, broad-shouldered, with a jagged dorsal fin cutting the water above him like a blade. His teal hair drifts around a face of sharp angles and sharper teeth, and his eyes—gold, predator-bright—are fixed on her with an intensity that makes the water feel suddenly still.

Behind him, the reef falls away into open water. He's alone. Which is either very brave or very stupid.