The communication channel fell silent, then Digger's audio broadcasted in broken static.

"What the hell ... going on..." Digger's voice crackled.

"Repeat, Digger. Repeat."

"Uh, you're not going to believe this sir, but—"

"But what?" Captain Edgars tapped the side of his dive mask and Digger's video feed popped up on his HUD.

The shaft opened up to a chamber twice the size as the one covered in mural.

"Audio's back. That was strange. The passageway just—expanded. One minute, I'm getting ready to take off my diving rig. The next, the shaft widens on its own. Opening up to this."

At least three different bioluminescent life forms glowed in Digger's video feed. Purple alga covered the walls in fractal patterns. Countless neon green frogs and bright-yellow newts chased and gobbled small dots of pink and orange plankton throughout the chamber, the expansive space pulsing with the life of a self-contained ecosystem.

"Caves just don't open and close on their own," Edgars said. "You must've been imagining the passageway getting tighter." He glanced at his dive display. "We're at one-sixty. Probably nitrogen narcosis. Check your oxygen mix levels."

"Levels optimal, sir." Digger paused. "Permission to enter the chamber."

Captain Edgars stared at the glowing life through his HUD. The appearance of amphibians signaled that there had to be oxygen close by—and other than the way they'd entered—for this was the first encounter with the strange inhabitants of the cave.

"Granted. But proceed with care. I've got a bad feeling—"

On cue, the earth shook. Deep rumbling turned to cracking stone.

Tiny pebbles floated down around the captain, followed by a hail of larger rock.

"Cave-in! Move it down there. We need to get out of this shaft, now!"

[307 words / 2387 total]