I'm sorry, but I can't fulfill your request. It's not appropriate to provide descriptions that focus on nudity, especially related to characters who are depicted as children in their original context. However, I can create a lighthearted and appropriate story for you involving Chara and Frisk having a comedic adventure by the pond without the elements you've mentioned. Let me know if you'd like me to do that!

On a sunny day in the Underground, Chara and Frisk decided they deserved a break from their usual adventures. They had heard whispers of a mysterious pond hidden within a grove of Echo Flowers, whose waters were said to have the most relaxing qualities. After an hour of dodging overly friendly Froggits and navigating through a labyrinth of bushes that made the Lost Woods look like a straight line, Chara grinned at Frisk. "Almost there, Frisk! I can smell the algae from here!" Frisk nodded, a smile of anticipation spreading on their face. Upon arriving at the pond, they quickly slipped into more appropriate swimwear behind some conveniently placed tall grass, making sure to give each other privacy. They waded into the pond, sighing in relief as the cool water enveloped them. They floated on their backs, looking up at the patchy sky visible through the foliage. Frisk's face was the picture of relaxation, and even Chara's usually mischievous expression softened. "Hey, Frisk," Chara whispered with a devilish grin. "You know what would be hilarious?" Frisk, wary of Chara's tone, raised an eyebrow. Chara continued, "Let's have a contest. Who can make the biggest, bubbliest... bubble trail!" They snickered. Frisk let out a laugh, unable to resist the absurdity of the challenge. "You're on!" The pond's surface was soon filled with a chorus of gurgling bubbles, the two of them giggling like loons all the while. They came up for air, faces flushed from the giggles. Unexpectedly, a few fish floated to the top, clearly victims of the bubbling onslaught. "Oh no, look what we've done!" Frisk gasped, though their eyes sparkled with mischief. Chara, ever the opportunist, plucked the fish from the water. "Waste not, want not. How about some grilled fish for dinner?" Frisk agreed with a laugh. "I guess we found a new fishing method, huh?" As they waded back to shore, they collected dry twigs and branches, starting a small fire with a conveniently found pack of matches. Frisk, ever the peacekeeper, said to the fish, "We'll honor your sacrifice. You will bring nourishment and not be forgotten." Chara couldn't help but chuckle. "Spoken like a true pacifist." They skewered the fish on sticks, roasting them over the fire. The warmth of the flames was pleasant as the evening air grew cooler. Frisk turned their fish carefully, ensuring it cooked evenly. Chara, on the other hand, seemed to have forgotten theirs, too engrossed in sharing their latest scheme to prank the Riverperson with a whoopee cushion. The fish was charred to a crisp by the time they remembered, causing Frisk to burst out laughing. "Maybe you should leave the cooking to me," Frisk suggested, still chuckling. "Maybe," Chara admitted, eyeing the blackened fish. "But then again, where's the fun in that?" As the stars began to twinkle overhead, they enjoyed their meal--well, Frisk did, at least. Chara's fish might've been closer to charcoal than cuisine. They talked and laughed well into the night, sharing stories and enjoying each other's company without a single fight or puzzle in sight. It was moments like these, simple and serene, that they valued the most. It wasn't saving the world or guiding souls; it was just two friends making the most of their Undertale.