"I don't know," Ryan said, still visibly surprised by her new voice. "It's awfully dark down there, and we don't know what's in there. Besides, do you really think it would lead anywhere we want to go?"
Johnny shrugged. "I don't know," she replied. "But I don't think we're going to get very far on land. We're unfortunately not built for it anymore. Besides, it has to lead somewhere."
"But what if there's something bad down there?" Ryan moaned. "If we die like this, would we be mermaids in Heaven? I know I don't want that."
Johnny chuckled in spite of herself. "I don't think there's anything down there that would eat us, Ryan," she said. "There's nothing in the pool for it to feed on. But if you're worried about getting hurt, you can follow behind me. That way you can turn tail and run if something eats me." She swam down to the tunnel entrance.
"Wait!" Ryan yelped. Johnny turned to face her. "I don't know about you," she said, "but I'm sure not spending my life in this stupid pool. You're free to follow me if you want." With that, she launched herself into the tunnel. Ryan followed shortly after, griping about getting killed and spending eternity as a woman.
The tunnel was quiet and the water much more still than the pool. It had the same feeling to it as a long-abandoned house; quiet and free of any apparent threat, but somewhat frightening nonetheless. This did nothing to abate Ryan's nervousness, but Johnny took a little comfort in the stillness of the water. After all, if it hadn't been disturbed in a while, that meant there was nothing around to disturb it.
The two mermaids continued down the tunnel as it grew steadily darker. Pretty soon, Ryan couldn't see Johnny in front of her, and added this to her list of complaints. "Listen," Johnny snapped, "would you just be quiet? If there was anything down here, we'd never hear it coming over your whining!"
Embarrassed, Ryan shut up, and the sisters continued their swim. Soon, it was dark enough that they couldn't see the walls of they tunnel, and they had to resort to feeling for the walls of the tunnel with their hands, which slowed their progress considerably.
Fortunately, it wasn't long until light returned to the tunnel. This time, however, it had a noticeable green tinge to it. They picked up the pace again, although they watched carefully to try and figure out when they wereg etting close to the source of the light, whatever that might be.
The light grew steadily stronger until the tunnel was bathed in a soft,40-watt greenish glow. Up ahead, the sisters could see the tunnel widen out into a small chamber, with whatever the light source was hidden in the left-hand side of it. Cautiously, Johnny swam up to the chamber entrance and poked her head in. After a brief survey of the chamber, she swam inside and motioned for Ryan to follow. After a moment's hesitation, Ryan did.
It was somewhat anticlimactic, really. The chamber was just a naturally-formed hollow in the rock, with a smooth, mirrorlike surface on one wall, in which the two could see themselves. They were quite a pair; Johnny was slender and girlish, her bare breasts comparatively small, while Ryan was busty and shapely, not to supermodel proportions, but enough to make a lot of women jealous. Their color schemes were also different; Johnny's cool blue scales and dark red hair matched her calm, collected demeanor well, while Ryan's emerald green tail and long, golden hair only went further towards making her look the part of the stereotypical panicky blonde she was acting.
In fact, the differences between the two were the most striking thing about the entire scene. The light source, by comparison, was almost mundane. It was an orb, set on a simply-carved pedestal - an orb the size of a bowling ball, with a creamy, translucent white surface, a green light emanating from within. It was the world's biggest frosted lightbulb, basically, and Ryan was a little disappointed.
"That's what we came all this way for?" she said. "A light?"
Johnny shrugged. "It was worth a look," she said. "Besides, it gives light, but that might not be all it does. Maybe it'll change us back. Maybe it'll turn us into something else. Maybe it's just an underwater nightlight. There's only one way to find out."
The two mermaids stared at the orb, wondering whether or not to investigate any further.