Author's Note: Okay, this is a WARNING : I've upped the rating for this last chapter... it's rated MATURE, so if anyone is offended by that, please turn back now! It contains sex... although not very explicit. It's also the last chapter, so I just wanted to thank everybody for their great reviews and encouraging words :-) I appreciate it very much. I'm sure you'll be seeing more Dasey fics from me in the future (I just can't seem to stop lol), so look for that! Alright, on with the ending!

Casey snapped her head over at the sound of Derek's voice. He was illuminated under the moonlight, standing there in his pyjamas with a smirk on his face. Casey waded over to him, her cheeks only slightly pink from having been caught.

"How's the water?" he asked, his eyes lingering on the parts of her body that showed above the surface.

"Warm," she said softly, wondering just what he was going to do next. She just watched as he stripped down in front of her, exposing his hard abs, leaving only his boxers on as he started towards her. He closed his eyes briefly as his body began disappearing under the water. It was warm from previous hours under the sun, just as she had said, and it felt really good.

He swam over to Casey, and silently they paused in the water, simply looking at each other, studying each other, daring each other to make the first move. To Derek's complete surprise, it was Casey who first reached over and touched him, gently wrapping her arms around his neck, but still keeping a bit of a distance between them.

Derek quickly grabbed hold of Casey's hips below the surface of the water, pulling her closer to him.

"Derek…" she began.

"Shhh," he stopped her, closing the space between them and capturing her lips with his own.

They both groaned simultaneously at the feel of their lips meeting. Derek slid his tongue into her mouth, kissing Casey deeply and she wrapped her legs around him under the warm water that surrounded them.

"I just…mmuh…wanted to thank you for coming after me yesterday…" Casey moaned out between kisses. She could feel Derek's body hardening against her as she ran her fingers through his damp hair.

"Well, this is a good way to thank me…" Derek smirked against her lips before capturing them again, sliding his hands up her bare sides to splay against her bare back that was half-submerged under the dark water. He ran his finger under the clasp of her bra, and when Casey didn't say anything, he swiftly unclasped it.

Casey felt her bra slip off of her but didn't stop Derek. She didn't want to. She began kissing down his neck as his hands came up to cup her breasts.

"So soft…" he murmured as he massaged her sensitive skin. He felt her lips latch onto his throat and begin sucking gently. He moaned and closed his eyes. The flew open again once he felt Casey's hands at the waistband of his boxers.

"Case…" he whispered, his voice thick with lust. "What are you doing?"

"Thanking you…" she murmured, detaching her lips from his throat and looking up at him. Even in the dark, he could see the desire in her eyes.

He swallowed harshly. "You don't have to do this…"

"I want to," she said softly, biting her lower lip. She had never wanted anything more in her whole life than she wanted him at that exact moment.

"We can't…" he drifted off. They could never have anything. They were stepbrother and stepsister. And Casey knew this. She nodded slowly.

"I know," she whispered, running her fingers through his hair again. "Let's just have this moment then." She wanted this. She really did.

Derek looked hesitant. He wanted it, too. So much. So he gave in, leaning down and kissing her passionately to let her know that he was game.

She smiled against his lips and her hands drifted down to the waistband of his boxers. She tugged at them, and he helped her get them off of him. He stepped out of them and the boxers joined her bra at the bottom of the shallow lake.

Casey reached out to touch him, but he stopped her, his hands moving to the last remaining article of clothing between them. He easily hooked his fingers inside the waistband and slid the panties down her long legs. He pulled her tightly to him, then, crushing her bare breasts against his chest, skin coming into contact with skin.

They were silent as Casey wrapped her legs around him again, linking her ankles together tightly so she had a good grip. Derek gently gripped her hips. She closed her eyes tightly and clutched at his shoulders, preparing for the next move. And Derek pushed himself inside of her.

Casey cried out in pain, and Derek quickly pressed his lips to hers to swallow any noises that might wake up their family. Her nails dug into his shoulders painfully, and tears slipped down her face, but Derek continued until he was fully inside her. He continued kissing her until she seemed to relax in his arms, her grip on him loosening and the tears rolling down her cheeks coming to a stop.

"You okay?" Derek asked breathlessly as he released her lips.

Casey nodded, the pain subsiding. She had known it was going to hurt, so at least she had been ready for it. Derek looked down at her a little worriedly. He had had sex before, but never with a virgin. He had figured that Casey was one, but wasn't completely sure about it, since she had been dating Sam for awhile.

Well, now he was sure.

"Go ahead," she gave him the okay, her arms wrapping around his neck.

Derek slowly began moving, getting Casey adjusted to his movements. And slowly, instinctively, she began to meet his thrusts, guided by his hands on her hips.

"Mmmuhhh….Casey…." Derek moaned, his eyes closing in pleasure. She felt so good.

Casey couldn't speak as she concentrated on their rhythm. It felt so… right. Her head tilted back as pleasure began to warm her body, and she felt like she was floating.

"Oh god, Derek…" she managed to breathe and his grip tightened on her hips in response, pushing himself deeper into her body.

They continued their mating until Derek felt Casey begin to twitch and knew she was about to let go. He quickly sped up the pace and shoved his tongue into her mouth. They kissed each other frantically as they released, swallowing each other's cries of pleasure.

When they were finished, Casey relaxed against Derek's body. He released her lips and hugged her to him, both of their bodies tingling. As their breathing calmed down and returned to a regular pace, Derek slid himself out of Casey and Casey released her legs from around Derek. They both stared at each other silently.

"Thank you," Derek found himself whispering to her hoarsely, his forehead mating against hers. He wasn't sure what he was thanking her for… giving her virginity to him?

But Casey just gave him a little smile. "That's my line," she whispered jokingly. He looked down at her with a smile playing on his face. And she brushed a light kiss across his lips before wading out of the lake and back to her tent.

The next morning, Derek and Casey acted as they normally do around each other. They bantered and fought. Neither of them mentioned what had happened last night.

It was like it had never happened.

Until…

"Ew!" Edwin came running out of the lake, looking disgusted.

"What is it, honey?" Nora asked as she looked up from making lunch for the crew.

"Marti found a bra in the lake," he said with a grossed-out face. The family looked over to the lake, where Marti was swimming around with her floaties on, using the bra as a slingshot. Nora muttered something about hormonal teenagers that sometimes use this campsite area.

And nobody noticed Casey's blushing cheeks and Derek's huge smirk.

the end ;-)