A/N: A response to this prompt on kinkme_merlin: Arthur/Merlin, hot springs episode! Because there totally are hot springs in England
And: Sulis is the Celtic name for Bath in Somerset.
"Aaahh..." Arthur breathed out in pleasure as he eased himself into the steaming waters of the hot springs. He heard Merlin pulling off his own clothes, and a few moments later, Arthur shut his eyes in reassurance as Merlin slipped in beside him.
"Got to give the Romans credit," Merlin said. "For building this on Sulis."
"Sheer genius on their parts," Arthur said, sighing as Merlin wrapped his body idly around Arthur's form in the heated waters. "I can't believe no one else has found it, yet."
Merlin started gently stroking his hands up and down Arthur's body as he said, "They say King Baldud discovered these waters' healing qualities..."
"I don't need to be healed," Arthur murmured as he sat himself on the stone bench under the water, leaving him submerged to the neck. Merlin settled himself in behind Arthur, wrapping his arm around the prince's torso. "Just...relaxed."
"Mmhm..." Merlin mumbled into Arthur's neck, as he pulled Arthur's back to his chest, leaning them both back as his head rested against the worn, aged tiles of the edge of the pool.
Merlin inevitably caved into his pathetically long standing instinct to take care of Arthur, his fingers unraveling from their interlaced grip to slowly start massaging his way across Arthur's torso, down to his hips, up the sides of his ribcage, and onto his shoulders.
Arthur moaned at that, and objected only slightly as Merlin pushed Arthur up, and prodded the man back into Merlin's lap, except this time he was straddling his servant, giving Merlin better leverage to massage his arms and shoulders, as Arthur buried his face in Merlin's neck, letting Merlin's magic fingers slowly work their way down Arthur's back, loosening his muscles and making him melt bonelessly against Merlin and not give a damn about it.
"How well," Merlin murmured into Arthur's ear. "Do you think water would work...as lube? Not like you ever use much, anyway..."
Arthur gasped as Merlin punctuated that with a probing finger around his entrance, in it, as Merlin murmured, "You're so...relaxed...already..."
Swallowing, Arthur pushed himself back and said, "I'm a prince...I'm ready for anything, always."
Merlin grinned at that, and his other hand reached down, as well, and Arthur quickly grabbed both of Merlin's wrists and held them in one hand between him and Merlin, using the other hand against the stone wall as leverage to lift himself up on his knees, looming above Merlin with a smirk.
"How ready are you?" Merlin asked.
In response, Arthur lowered himself on Merlin's erection.
Merlin gasped as Arthur took him into his body, stopping not even once until Merlin was embedded in him straight to the root.
For a few moments, it hurt - maybe he should've let Merlin stretch him some beforehand - but then Merlin writhed beneath him, and Arthur rolled his hips in response, and, with the right angle, it suddenly didn't matter that Merlin hadn't stretched him at all.
Merlin got his hands free of Arthur's grip, but was now just sliding his hands across Arthur's chest, under the water, shoulders slick with sweat and steam as he kneeled up, and dropped down on Merlin again, using his now free hand to hold Merlin's hips down.
It wasn't fast, but the rhythm was steady, and Arthur angled his hips so Merlin rubbed that right spot in him every time, and, and-
When Arthur came, his seed diluted and dissipated quickly in the water as he stalled and writhed, clenching around Merlin and throwing his head back as a few thrusts later, Merlin followed suit, clutching Arthur's shoulder and hip in a grip that was sure to leave bruises, and Arthur couldn't care less about that, either.
Panting through the afterglow and heavy steam in the air, Arthur melted into Merlin's embrace against, as they let the warm water undulate around them, relaxing them on the way.
"Yes," Merlin muttered. "Those Romans were sheer genius, indeed."