She goes swimming in her underwear

In what felt like just a handful of minutes, the group of five made it to the destination. It was a small, mostly rocky beach area, sandwiched in between the river and a dense patch of trees. The cool blue water looked just as lovely as it had the day before, when Mackenzie had been tempted to go skinny dipping. And though she desperately wished to jump in and cool off again, Mackenzie was far from alone this time. Though equally without a bathing suit. Once again kicking herself for not bringing anything with her, Mackenzie mentally vowed to keep her bikini in her backpack for the remainder of her camping time.

"All right," Audrey said excitedly, "we made it!"

The rest of the group jovially began disrobing, quickly demonstrating that they'd all been wearing swimsuits underneath their clothes the entire hike. Nicole and Audrey were both wearing bikinis, with Nicole's being more than a little bit skimpier than her friend's. Ben and Mike were likewise both sporting swim trunks on their lower halves instead of shorts. Mackenzie felt awkward and embarrassed for being so unprepared yet again.

As Audrey, Nicole, and Mike began setting out their towels on the rough shore, Ben glanced at Mackenzie and said, "Don't worry, Mackenzie. You can just keep that towel on. I don't really need it."

It was something about his final comment that finally settled Mackenzie's internal debate. These people had been nothing but friendly and welcoming to her, and they'd only met her yesterday! Was she really going to make Audrey stay on the shore with her and ruin her swim time? Not to mention the fact that they'd already seen, well, everything. So really, what was the point in feeling shy about flashing her underwear now?

"Y'know what?" Mackenzie asked aloud. "It's fine. I can just take a dip in my underwear."

Then, in one deft motion, she unfastened the towel around her hips, revealing her panties once again, and handed it back to a very surprised Ben. But Mackenzie wasn't done there. She immediately followed that up by tugging off her tank top, revealing the white bra underneath. Everyone was a bit awestruck as Mackenzie stood there in just her underwear, a small triumphant smile on her face.

"Holy shit she's actually doing it!" Mike excitedly whispered, mostly to himself. But Nicole heard him too, and shot him a cold look that he didn't even notice.

"I mean, it's really not any more revealing than a bikini, right?" she asked, trying to sound more confident than she felt.

Amidst the gobsmacked faces of her new friends, Mackenzie failed to noticed the less-than-thrilled expression of Nicole as the dark haired girl registered Mike's particularly enthusiastic grin. Mackenzie was too busy trying to convince herself she had nothing to be embarrassed about.

"Well? What're we waiting for?!" Mackenzie happily said before turning to run towards the waiting water. The rest of the group quickly followed suit, rushing to catch up with the exuberant redhead. Ben, Audrey, and Mike were cheering and shouting.

Nicole, meanwhile, was silently staring daggers at the perfectly round butt bouncing along in front of her, encased in those little yellow panties. She was now positive that Mackenzie was an exhibitionist slut, who was likely also trying to steal her boyfriend away, given how much Mike had been drooling over her so far. Well, she couldn't have that happening, now could she?