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Waves crashed up against the rocks, spilling over Tony’s bare feet as he picked his way across them to the cove. The water was cool and inviting compared to the sun-baked rocks. It pulled him forward despite his apprehension.
These past few weeks had been a dream-- discovering Steve, helping him, learning about him-- it had all been unreal. Each morning he opened his eyes prepared to relegate the memories to pure fantasy, yet the line of shells and shiny bits of metal on his nightstand, each given with increasing reverence, said otherwise.
Then yesterday came the most precious gift of all: a piece of sea glass the same shape and color as Tony’s arc reactor. When Steve presented it to him, his nervousness and hopeful pride were on full display on his face. It meant something to Steve, something that almost frightened Tony as much as it intrigued him.
Fins flashed at Tony from the water, bright blue and red with pearly white stripes. Tony hesitated, having expected to see Steve’s usual silver coloration.
A blond head popped up from beneath the waves and called to him, eerie and melodic human words mixing in with whistles and crackles. “Tony, please? Want.”
Thrumming with anticipation, Tony traversed the last few feet to the water. But when he reached the edge, he stopped, fingers tangled in his shirt, uncertain if he should take the next step.
Tony should just climb back up to his mansion and pretend this never happened. It would be better for both of them. He was sure what was on offer here was significant to Steve, more than just a bit of casual inter-species experimentation. It was a commitment.
Steve creaked questioningly at Tony.
“I can’t believe I’m doing this.” Tony whistled back at Steve, which never failed to delight the merman.
With a dopey smile, Steve sank lower in the water and began blowing bubbles towards Tony. Biting his lip to keep from smiling, Tony stripped off his clothes and slipped into the warm water.
Steve was next to him as soon as he hit the water, nibbling Tony’s fingers and toes. The light nips just barely stung, but they took Tony by surprise, distracting him enough that a wave washed over his head.
“Ow! What are you doing?” Tony spluttered, when he came back up.
Steve just grinned with his too-sharp teeth and nibbled on Tony’s toes. This was a game , Tony realized with an unexpected thrill. He pulled away, dolphin kicking through the water, but Steve kept pace with him easily. A little offended at how easy he made it look, Tony switched to a breaststroke and picked up his speed.
It wasn’t long before Tony tired and slowed to a stop. “I need a minute,” he huffed between gulps of air.
Steve swam around him in tight circles while Tony caught his breath.
Tony laughed breathlessly. “I get it, you’re faster.”
Surfacing, Steve bumped his nose against Tony’s and whispered Tony’s name in that ethereal voice of his. Tony sucked in a breath as shivers raced down his spine.
He was yanked down under the water before he knew what was happening. Instinctual fear sent his heart pounding as he struggled against nothing, unable to tell up from down. He forced himself to calm and just float there while he gained his bearings. Steve smiled and swam around him, brushing his tail in a figure eight along Tony’s belly.
“Want, want, want Tony,” Steve chanted, his voice somehow clearer underwater.
Tony reached out for Steve, trying to catch hold of his tail, but as soon as he had it, it flicked out of his grasp. Instead Steve’s arms wrapped around Tony’s chest and Steve pulled them up to the surface in one shot.
Steve flipped Tony over so he was resting on top of Steve with his head and shoulders above the water. They stayed floating there, undulating with the motion of the waves.
Tony smacked Steve’s chest. “You–you’re such an asshole. I thought I was going to drown!”
“Want Tony,” Steve said with pleading eyes. A slit had begun to open a few inches below Steve’s stomach. With a thrill, Tony realized he could see something soft and pink inside. Steve quivered his tail against him and asked, “Tony want?”
Tony hung his head, defeated. “Urgghh, yes, Steve. I want you too.”
The slide of Steve’s scales over Tony’s skin, all across his thighs and pressing against his balls and cock, shouldn’t have been erotic. Yet a heat was building deep inside Tony with every wave, slow and fierce.
Tony cautiously ran his fingers around the edge of the slit. “How’s that?”
Steve blew a few pleased bubbles Tony’s way. Tony grinned and continued, gently probing until Steve’s cock slid out. It was slick with some sort of water-resistant fluid. Grinning at the discovery, Tony coated his fingers in the stuff and reached behind him to slide one inside.
“Nnn, I forgot how fun this could be,” he mumbled while working himself open.
Steve, for his part, seemed content to just watch him, his hands occupied with holding Tony above the water. When Tony decided he was loose enough, he slid forward and lined up his ass with Steve’s cock. Steve pressed in, slowly at first, with the hot length taking him fractions of an inch at a time, only for the entire thing to slam home halfway through.
Tony’s mouth fell open. “Ungh! Yes!”
With a bubbling laugh, Steve slowly slid back out before pounding his cock even deeper inside Tony. Tony gasped for breath and noticed they were sinking. Their frantic motion was causing them to slip further down. Tony straightened up and held his head as high as he could. It was just barely enough to keep his head above the water while Steve fucked into him from below. He couldn’t stop, not yet. This feeling, this rush of bodies against each other, Steve , was something he needed more than air.
He chased the feeling further, drawing Steve up for a kiss. Steve seemed confused at first, unsure how to respond to the press of Tony’s lips, but he soon figured it out, mirroring Tony as he explored Steve’s mouth.
Steve came like that, finishing inside of Tony with a shiver while Tony kissed him. Tony knew he was on the edge too, so he took his cock in hand and pulled himself off. He came with a shout, his semen lost in the ocean’s waves.
“Tony, love,” Steve whispered, bumping his nose against Tony’s.
Tony slumped over, collapsing against Steve’s chest. The frenzy, that burning desperation for more, passed, leaving him feeling wrung out. He hissed as Steve pulled out, his ass stinging from the salt. An exhausted smile formed on Tony’s lips.
“Yeah, me too.”