He takes care of himself

Marcus gives Allison a long, blank stare. The wheels seem to be turning for his thought process. Allison realizes that there is NO WAY a boy is going to say no to a blowjob. She thinks better of that whole possibility.
"I'll distract Will. You take care of...that." She says with a glance downward that makes her stomach flutter. How could they have gone this way so quickly, she thinks as she leaves Marcus and moves to the clearing and the campfire.

~ She leaves her dark, watery den. Streaking through the clear lakewater before the sun goes down, she is aware of the water and its many chemical balances. She abruptly stops as she nears a shore, sensing a reaction to her previous call in the lake. She changes direction and comes up to the shallows near the stony cliffs and flat beach. There is the scent of a mate in the water here, he travelled around in the water accepting her pheromones for some time, and then went near the shore with a rival female. There she finds semen in the water, this could be the source to fertilize her clutch, waiting in the cave. The smell of their sex follows them above the water's surface. She emerges from the water, her smooth skin is sleek and shiny in the waning sunlight, and follows the scent into the nearby woods. She will assess the male first hand, and bring him to the clutch soon if he pases muster...

~While Allison goes to talk to Will, Marcus bolts to the tent. Utilizing the tent for cover, he runs around from the woods-side, not coming into the light cast by the fire. It is dusk, and inside the tent it is practically pitch-black. The better to use his imagination, he supposes. Groping in the darkness, he finds a sleeping bag(hopefully his). He pulls the lanyards and looses it from its coil, quickly spreading it out on the tent floor. He lies down on the silky sheeting and closes his eyes. Immediately the picture of Allison's round ass is fixed in his mind. The thought of bending her over and ramming into her repeatedly, and hard, soon follows. He begins to stroke his erection and wonders absently if the asshole is out of the question for Alli. Well, it doesn't have to be in his mind! His thoughts turn to breaking in her tight ass, her imaginary wails soon turning to moans of pleasure. Gritting his teeth, he squeezes his shaft tighter, thinking of her tight butthole around the shaft as he pushes it all in. A moan inadvertantly escapes him as he speeds his pace.

~She moves to the site of the glowing spot, two of the people are close to the hot bowl with smoke pouring out. The heat is a bit unpleasant, and being so far from the water her skin is developing its protective slippery coat of slime, but finding the mate is worth it. She sniffs the air, and the smell of mate is near. A strange thin cave stands close to the hot spot, mate inside, judging from the smell and sound it emulates. Moving into the tent, her pheromones start to project again. She slides inside, the rythmic slamming of a fist on his member catches her attention. Quickly and soundlessly she slides to the floor and between his splayed legs.

~"Just...About...there...Alli, your asshole is sooo tight, fuck, I'm gonna...gonna" Marcus whispers to himself. Suddenly, there's a wet body pressed against his thighs and slinking against his balls. 'Wet' is not quite the word for it, more like 'slippery'. The warm feeling from the lake is back.
"Allison, that you?" He croaks, barely above a whisper.
"SHHHHHHHHH." is the reply. A bit too loud to be a proper shushing, and something odd about it. What about this trip has been normal though? 'Allison' crawls over him, and her hand wraps around the hand he has on his shaft. She starts pumping it up and down. He was already close, and he throws his head back and shuts his eyes to hold out. His other hand slides onto Alli's back, she seems less fleshy, more muscular. Her boobs are slippery and firm, not as jiggly as before, but it's gotta be her, coming to 'help him out', who else could it be?
The warm feeling engulfs him as he lets go of his dick and lets her take hold, both of his hands frantically roaming her body. He's groping, squeezing, rubbing her taut form. Damn, Alli's ass seems tighter too, not as easy to hold, but puckered. She keeps jacking hm faster, his moans escape more, he can't help it, who could!?

~Will is sitting, tending the fire when Allison comes back.
"How was the swim?" He asks earnestly, he looks up at her."Holy crap! You're gonna catch a cold like that! Get some dry clothes on!"
"I'm okay" Allison responds, looking over at the one tent they brought to 'save space' whilepacking the car. Thinking it wasn't such a hot idea anymore. Will brings her a towel from the car's trunk, and throws it over her shoulders. He doesn't even notice my nipples through the shirt, Allison thinks. That is how this is supposed to go, just friends. A moan comes from the nearby tent. "Dammit Marcus", she curses to herself.
Will doesn't hear, thank goodness!
"Well, I was saving this for later in the trip" Allison starts, realizing she may need help to ease the situation. "But I guess this is as good a time as any."
She goes to her bag, set over by the trees, and brings out a bottle of Tequila.
"Filched it from my dad's cabinet, I think Marcus can catch up."

~Marcus is gritting his teeth against an explosive ejaculation, and 'Allison' changes up again. Letting go of his throbbing member, she puts both hands in the center of his chest, pushing him against the ground, and raises her lower half, putting her feet on either side of his hips, she lowers her hot snatch down to meet his cock, sticking straight up in anticipation. Without any trouble, she lines up and his dick sticks straight in! She lowers all the way down the shaft until their crotches mash together. This CAN'T be Alli! It hardly matters now! She starts to lift and drop herself, riding his shaft. She does this less than ten times, and he lets go! Unloading a massive amount of spunk into her and grunting while he desparately tries not to yell out! She regards him calmly, pulling off and letting the rest of his cum spurt onto his belly.
"SHHHHHHH." She says, and darts from the tent. The slime from her body covers the sleeping bag.
"Shit" says Marcus to himself."gotta clean up." Panting, he gets to work.