Monster Falls

Finding Fluvius; Chapter 1

"Hey Dipstick!"
"Hm?" Dipper Pines looked up from reexamining the journal in his hands. His eyes glanced at his sister, Mabel Pines, from between the brim of the book and his hat. Mabel, wearing her blue seapony sweater, had pulled herself over the counter of the Mystery Shack.
"Dipping Dot, Wendy says she found a really cool river out in the forest, but she wanted us to be with her before she explored!" Mabel exclaimed. "She said it was really clear, so she told us to bring our bathing suits."
Dipper 'contemplated' this for a minute, but had already made up his mind.
"Um, sure, I guess." Dipper closed the Journal and stuffed it in his vest, jumping off the seat and following Mabel out the Mystery Shack door. Wendy was waiting outside the door, leaning against the wall.
"Wait, shouldn't you be at work?" Dipper asked. Wendy shrugged. "Eh, it's a Sunday, Stan won't mind if I take off a little early. Now come on, that river won't wait for us!" Wendy said, heading off toward the river with Mabel and Dipper in tow.

After almost and hour, they stopped to rest.
"Wendy, I know this river is supposed to be amazing and all, but-" Mabel pauses to take a breath. "Are we almost there? It's been, like three hours!"
"Mabel, it's been one hour."
"Shush, Dipper, I'm trying to make a point."
Wendy smiled. "Don't worry, we're almost there. And trust me, it'll be amazing! You won't regret this."
Dipper fanned his red face with his hat. "Are you sure?"
"Yeah, dude!"
Dipper shook his head and they continued their trip.
After less than ten minutes, Wendy stopped. She held her hand out like she was about to separate the bushes.
"We have arrived at our destination." She said like the Google maps lady, and pushed the bushes away. And true to her word, the hour-long tread was worth it. Mabel and Dipper stared breathlessly, from walking and the beauty. Before them, was a large, clear lake with a soft glow, and the beach was a vibrant sandy yellow. The river bottom looked like it had diamonds embedded in it, but upon reaching their hands in, it was soft and smooth.
"It's.. wow!" Mabel exclaimed.
"I know, right!"
"But.. how'd you find it?" Dipper asked as they sat on the shore.
"Oh, me and Soos got lost in the woods and found this place."
"You were lost in the woods for an hour?" Mabel asked.
Wendy shrugged. "We drove, like, halfway there and Soos' truck broke down."
"Oh. Fair enough. Let's swim!" Mabel tore her sweater off, revealing her swimsuit, and jumped in the water, splashing Wendy and Dipper.
"Hey!" Wendy tore off her jeans and jumped in, not wearing a shirt over her swimsuit in the first place. Dipper dodged Wendy's splash, knowing it would happen. He took off his vest, shirt, socks and shoes, and hat, placing them far enough away they wouldn't get splashed, and jumped in after the girls.
During a splash war, Dipper happened to get dunked under the water and ended up drinking some. Coming up, he swam to the shore and shook his hair out, combing it through with his hand. Natural river water couldn't taste so sweet, could it?
"Hey, Dip Stick! Why aren't you enjoying the water?" Mabel asked, climbing out beside her brother.
"It's nothing, I just- hey, could you do me a favor?"
"What is it, bro-bro?"
"Just, um, taste the water for me?"
Mabel looked questioningly at her brother before taking a handful of water and taking a sip. Her eyes went wide for a second before she drank all the water in her hands.
"Dip, this water's so sweet!"
"I wasn't imagining it- why do you think it's so sweet?"
"I dunno, but Wendy!"
Wendy turned around in the water, her attention snapping to Mabel and Dipper.
"Drink the water!" Mabel shoiyey and Wendy did indeed drink it.
She swam back to shore and sat between the twins.
"It's sweet- why do you think it is?" The twins shrugged.
"Well, let's not waste the rest of the day!" Mable said, splash the others.
"Oh it's on!" Dipper said, and the splash fight continued.

They had lost track of time and before they knew it, the sun was setting.
Wendy groaned. "Great. Who knows what would be waiting for us in there. And at night, no less! At least it isn't that dark."
"What do you mean? It's getting really dark, Wendy." Mabel questioned. The three were sitting on the beach and drying off, beginning to get their clothes back on.
"Hmp. I guess it's just me then." Wendy shrugged. The redhead turned her head around. "Did you hear that?" The twins shook their heads. After a few minutes of putting their clothes back on, they heard a faint "Kids!" from the forest.
"Stan?" Dipper yelled back.
After a few minutes of yelling back and forth, Stan and Soos emerged from the forest in Soos' truck.
"Kids!" Stan climbed out of the truck and hugged the twins, completely forgetting Wendy.
"Oh, am I nothing to you?" Wendy asked with a smile on her face.
"Hey, you lost my great niece and nephew in the forest!" Stan shot back.
"Okay, one, I was with them, and two, I know exactly where we are! We just lost track of time."
Stan snorted.
"Grunkle Stan, you should've came with us! The water was so sweet and just the right temperature!" Mabel exclaim.
"Sweet water? Hm. I could make a buck or two off of that."
"Oh no. Look what you did, Mabel."
"Excuse me for sharing good news with our Grunkle, Dipper."