releasing an attenuated breath and swinging my light upward through the swarm of ascending bubbles. In lightless blue holes, animals like this inch-long Agostocaris cave shrimp don’t need ...

Exposures were long, as much as five minutes. Because it was so early, light coming out of the cave was an incredibly rich, predawn blue. Light from the flashlights was a glowing yellow-orange.

The show, called “Ao no Dokutsu (blue cave) Shibuya,” features about 600,000 blue LEDs along an 800-meter stretch between Shibuya Koen-dori street and rows of zelkova trees in Yoyogi Park in ...