If she succeeded in destroying it with her golden sword, the little band of fugitives might then swim through the opening into the clear waters of the ocean.

Although this prince of the sea devils was said to be big and wise and mighty, there was but one of him to fight; whereas, if they attempted to escape through any of the passages, they must encounter scores of such enemies.
"Swim straight for the opening in the dome!" cried Aquareine, and in answer to the command, the four whisked their glittering tails, waved their fins, and shot away through the water at full speed, their course slanting upward toward the top of the dome..