Below roughly 1000 metres the ocean enters the aphotic zone — water so deep that no sunlight survives and the only illumination is cold biological light. Marine bioluminescence peaks at 470–490 nm because blue-green travels farthest through seawater, so the abyss reads as electric cyan glow against a near-black field.

This system borrows the language of submersible instruments and ROV camera feeds: emitted light, never reflected; sparse pinpoints and soft halos rising from depth; sonar and depth-gauge readouts. Glow is precious and rationed, the dark is the dominant material, and every surface behaves like something seen through cold water.