Suddenly there appeared ahead of them a faint, bluish gleam upon the water’s surface. It was something elusive and unreal, and vaguely menacing.
“Daylight!” exclaimed young Mô eagerly. But Grôm said nothing. He did not think it was daylight, and he was apprehensive of some new peril.
The strange light grew and spread. It was evident now that it rose from the water, and also that it was advancing rapidly to meet the astonished swimmers. After a few moments it was bright enough in its blue pallor to show the swimmers that they were traversing a vast hall of waters, whose roof was lost in darkness. Some fifty yards ahead of them, and a little to the right, a low spit of rock, half awash for the greater part of its length, ran out slantingly from the wall of the stupendous chamber.
Toward this ledge Grôm now led the way, hurling himself through the water on his side at top speed. He could not fathom this mysterious phosphorescence, and he wished to get his people out upon dry land before it reached them. But fast as the adventurers swam, the ghostly radiance spread faster. Before they got to the ledge, the light was all about them; but it seemed to be coming from a great depth.
Nervously they all glanced down, and a low cry of horror broke from their lips. The depths were 240 swarming with monstrous, luminous forms, a moon-bright, crawling, sliding field of claws and feelers, and broad, flat backs, and dreadful, protruding eyes.
The eyes all stared straight up at them with a fixed malignancy that froze even Grôm’s blood. They seemed innumerable, and all together they came suddenly floating upwards.
Already the fugitives were dragging themselves out upon the ledge, in frantic haste, when the diabolical swarm reached the surface. But Hobbo, who was the slowest swimmer, was merely clutching at the rock when the water boiled all about him in a froth of light. A pair of huge, pincer-like claws seized him by the neck, and another pair by one arm, plucking him back. His convulsed face stared upward for an instant, and then, with a choked scream, he was dragged under. He disappeared in a swirl of pale blue, frantically waving claws, and eyes, and feelers, and black-fringed, chopping mouths.
Beside himself with rage and horror, Grôm stabbed down wildly into the whirling struggle, and his example was followed at once by Loob and young Mô. Some of their random blows went home, and as one or another of the gigantic crabs turned over in its death-throes, its nearest fellows seized it, tore it to pieces, and devoured it.
But A-ya, who had taken no part in this vengeance, now snatched Grôm by the arm, shrieking wildly:
“Look! They are coming out!”