For a while Deanna stayed quiet and neck deep in the water until Todd whispered to her, "Relax... We do this all the time. You have a guilty look on your face for no reason. Are you embarrassed to be swimming naked with them here?"

"No... It's not that, but..." and Deanna couldn't think of the right words. How could she explain that, even though, on rare occasions, her father had seen her in panties and a top, but her mother would always tell her to "Go put some clothes on!" because her father was there? Todd's parents were just the opposite. She had just watched them strip down and jump in the river naked with their naked kids and didn't seem bothered by it in the least. Polly had even commented about her father's apparently stiff cock.

“"Just relax... It's all good. As long as you aren't bothered by being naked in front of them there's no problem. They don't care if you're naked," Todd explained. Deanna smiled and finally began to relax.

After a short time Todd's mother announced they were leaving. She and her husband had been kissing in the water. The two walked out of the water hand in hand, picked up their clothes, and walked toward the cabin. Again Deanna was surprised. He was rubbing her ass as they walked away. No doubt he was hard as well, but she couldn't see that. "They'll be busy for the rest of the night," laughed Heidi.

"Are you trying to poke me in the butt?" Heidi giggled, bringing Deanna's concentration back to reality.

"Nope," Polly giggled. "He can't be because I'm holding his thing."

"Then it must be his finger..." Heidi replied softly.

"That's nasty!" Polly gasped.

"It actually feels good," Heidi contradicted.

"Really?" Polly asked in all seriousness.

"Yeah... Todd, show her," Heidi sighed.

Todd reached out to Polly and she let him pull her into his chest. "Wrap your legs around my waist," he told her.

"OK..." she answered in a soft voice. After a slight hesitation, she added. "Don't put your thing in me."

"I won't," he assured her. "Just relax..."

Deanna watched as Polly put her head on his shoulder and closed her eyes. She probably should have been mad with her boyfriend doing things to his 13 year old sister, but strangely it turned her on.

"It feels weird..." Polly muttered. "It's not bad, just weird."

"Are you fingering her butt?" Deanna mouthed to Todd. He nodded. Polly was just staying still with her head just leaning on Todd. "I like it in the butt," Deanna said to Polly.

"He put his thing in your butt?" Polly asked as she lifted her head and looked at Deanna. Deanna nodded and was getting hornier by the minute. "I don't believe you," Polly added as she moved away from Todd.

Deanna reached for Todd's hand and walked toward the shore. "If you don't fuck my ass right now I'll scream," she whispered to him.

As soon as they hit the water's edge, Deanna dropped to her hands and knees. When Tod knelt behind her, she lowered her head presenting her ass to him. "Ohh..." she moaned as his cock entered her.

Her eyes were clamped shut as her ass went from hurt to quickly pleasure. As her eyes opened again she saw Heidi sitting in front of her, knees wide open, as she rubbed her pussy. "That's so sexy," she muttered.

Deanna watched Heidi masturbate, both looking at each other's eyes, until Deanna became aware Polly was next to her. She looked to her side and saw Polly in the same position she was in. Todd's hand was behind her ass and Deanna suspected he was fingering her ass again. Polly's hand was between her legs.

The sex distracted Deanna and she stopped watching. Her climax was close. Todd suddenly lunged forward and Deanna felt his cock pulsating in her ass, signaling his climax. It triggered hers and she exploded. It took only seconds, but it felt like hours, before both she collapsed and Todd rolled off her. Heidi was furiously rubbing and Polly had rolled onto her back and was rubbing as well.

For a while all four remained still and silent. It was Polly who broke the silence. "I can't believe I did that in front of everyone."

"You must have liked it," Deanna commented.

"My butt's a little sore," Polly blushed.

"Mine too. Let's go swimming again," Deanna suggested.

The two stood and walked to the water. They didn't swim, just ducked down until they were neck deep squatting in the water. "I've never done anything like that... We've fooled around some, but he never touched me like that," Polly confessed.

"Are you OK with what happened?" asked Deanna.

"Yeah. It was fun watching him do your butt," replied Polly.

"No, I mean what he did to you," clarified Deanna.

"I guess... Are you mad at me? He's your boyfriend and my brother. We're not supposed to do stuff," sighed Polly as she hung her head down.