The ROV skims forward along the dark basaltic flank of the seamount, its hull lamps catching silvery flashes on myctophid flanks and the glassy margins of siphonophore chains no more than a meter away, while everything beyond dissolves into a monochromatic cobalt blue that deepens steadily toward black. At roughly 330 meters the pressure exceeds 34 atmospheres, compressing swim bladders and shifting the acoustic backscatter signature of the aggregation in ways that once fooled wartime sonar operators into believing they had found the seafloor — the same "false bottom" illusion that gave this biological phenomenon its name. Lanternfish, krill, and translucent shrimps lift off the seamount contour in loose volumetric sheets, using the topographic barrier to aggregate before beginning their nocturnal ascent of hundreds of meters toward surface feeding grounds, one of the largest daily animal migrations on Earth. Marine snow drifts through the lamp beams like cold suspended dust, each particle razor-sharp against the darkness, and deeper in the frame — beyond all artificial illumination — a few blue-green bioluminescent pinpricks flicker and vanish, the only light that has ever belonged to this place.
Deep scattering layer