For a request I saw on tumblr, I filled it for fun! Here's a bit of shower sex, with a twist! Haha, I hope ya'll enjoy this little drabble. PURE SMUT AND A TOUCH OF FLUFF AT THE END.

"A-already? W-w-wait, Rivai—mmfff!" Eren didn't have much of a chance to react as hot lips pressed roughly against his own, calloused hands going immediately to his bare and slim hips. The teen whined, melting into goo by the other's heated touch.

It was a school trip to the beach. There were lots of underwater caves and magnificent waterfalls in the area, so Rivaille thought he would treat the senior to something a bit risque than normal. They had decided to go skinny dipping in a hidden pool next to a waterfall because the water there was said to be good for your skin. Despite Eren being embarrassed by the lack of clothing, the P.E teacher managed to coax him into it.

After a while, Eren decided to go under the waterfall, but Rivaille wasn't done with him. "It's almost like sex in the shower, huh?" The older male asked, pushing the teen against the rock wall. The water cascaded over them, slicking their bodies up with the clear and cold liquid.

"R-rivai…lle…san…" Eren whined, letting the other worship his body with greedy hands and a hot tongue. He felt the other's tongue against his hardened nubs, causing him to cry out in pleasure. "Ngh..ah…" His hands held on tightly to dark locks, leaning his head back as the other made it's way down a tanned torso.

The teacher continued his assault, kissing, nipping, and licking every inch of flesh as if it were a dessert, not want to leave anything untouched by his lips and tongue. He tasted the dimple inside Eren's bellybutton, sharp eyes gazing up at the frazzled teen who couldn't form complete sentences anymore.

"Hnn." He grinned at the other's reaction. "You seem more sensitive than usual." Rivaille smirked, licking lower and lower, watching the other's face grow redder each second. He let out a small chuckle.

Eren looked down, covering his face with one arm as if to attempt to hide his blush. "It's…because w-we're in public…under a w-waterfall…" He was cut short as the teacher's hot tongue licked under the base of his leaking member. "Ah! Nng…hah…ahnn.." His moans echoed off the rock walls, but Rivaille knew for a fact they wouldn't be found.

Quickly losing his patience, Rivaille slipped a finger past the tight ring of muscle as his mouth fully sucked on the boy's length, the moans and whines from the other making his own need stronger. Fuck…no matter how many times we do this, he's still as tight as ever. Rivaille let out a groan, continuing to suck on Eren while adding more fingers into his ass.

"The waterfall feels good, huh?" Rivaille let the length out of his mouth and he licked his lips. Eren was a blushing and moaning mess still, probably not even able to talk. Shit…this kid is too cute…"It will have to do since we got no lube." Eren's eyes opened as his position was suddenly changed. He was facing the wall and his ass was sticking out and in the air, vulnerable.

"Uwaa, S-sensei! W-wha—" Those fingers were back, stretching him wider. Rivaille didn't want to cause him much pain. "Nngh…fuu….ahn…R-rivaille…hah…" The teacher couldn't wait any longer. He wanted to hear the teen moan and scream his name.

Rivaille stood up, his hands on slim hips. "I'm going in, Eren." He warned before pushing his own leaking cock inside the pulsing and tight flesh. Both of them groaned at the sudden pleasure, bodies shaking a little, Eren's fingers curled into fists against the rock wall, biting his lip. The pleasure was almost too unbearable.

"Ahn! R-rivaille!" He cried out as the other pulled out only to slam back inside. The pace began to pick up quickly and the waterfall continued to pour down onto their bodies, covering them with an erotic slickness. It was ten times better than sex in the shower.

The teacher let out low groans and moans, amazed on how the other was practically sucking him to a point where he thought his dick would fall off. "Shit…so tight…Eren…" He groaned again, fingers digging tanned flesh, probably leaving purplish marks there. The teacher couldn't help himself as he pounded almost mercilessly into his lover, biting his lip as he looked down an the round mounds hugging his throbbing length. It was almost too erotic for the older male.

"Ngh…Rivai…g-gonna…c-cum…" Eren moaned, turnings his head back so he could lock eyes with the other. The teacher nodded, keeping his heavy gaze on the other.

"Mmm. Scream my name, Eren. I want your voice to be…burned bright onto my brain." Eren nodded, drool spilling from his lips as his tongue hanged out with ecstasy. Soon enough, the teacher's name was screamed loud as his white seed shot out of him, splatting on the rocks beneath him. His hole clenched even tighter, and Rivaille couldn't hold out any longer.

"Fuuu….Eren!" He spilled himself inside the other, filling Eren with the milky white liquid. Rivaille groaned, leaning his chest on top of Eren's back. He could tell the other's legs were shaking and he probabaly couldn't stand any longer. He slipped his member out of the other, watching almost mesmerized as the cream-like substance slowly dripped out of the ring of muscle. Slowly he sat down on the slippery rocks, bringing the tired teen into his lap.

They both sat there, naked and wet, letting the cool waterfall clean them off. Rivaille's head rested against the student's shoulder, eyes closed. Eren was panting a little, but he grasped tightly onto the teacher's hands which were resting comfortable in his lap. The waterfall was relaxing, almost lulling them both to sleep.

"Should we go back to our blankets, sensei? It's getting dark." Rivaille's eyes opened lazily to look up at the sky, noticing that indeed the sky was darkening, preparing for the night. With a groan, he nodded, helping them both up. Both of them walked along the rocks, hand in hand, venturing to a cave which was warm and hidden from view. They had assembled blankets and towels there earlier, so they didn't have to do much work. They laid down on the ground, Rivaille pulling the teen into him, arm around his tanned and bruised waist. His fingers ghosted over the scars, trying to will them away with his touch.

Eren smiled and clasped his own hand against the other's. "It's okay, sensei. I like those….they're kind of…" Eren's face heated in embarrassment. "Erotic…" He whispered, glad his head was turned away from the teacher. However, that didn't last long as Rivaille rolled the both around so their faces were close together, noses lightly brushing ahainst each other.

"When you say that, it makes me want to fuck you again." Eren's face looked scared, but the man was only half-joking. "I know you're tired, so get some rest. We'll wake up in the morning and meet up with the other's okay?" The teen nodded happily, pressing his lips lightly on the other's nose.

"Good night, sensei! I love you!" Rivaille smirked.

"Ah, me too." He brought the blankets over them a bit more. "Good night, Eren."