The cavern air held an unmistakably fresh scent, being a close walk to the surface where the pine trees on the mountain side were. Yet the entrance from outside world was hidden behind thick, snowless pine trees; one could mistake the entrance to the cave as a dead end. In the cave lies a pool of water, isolated and lifeless, yet clear and cool, pure save for the rocks that it erodes. Gaps on the top layer of rock above the water let light into the otherwise dark cave,

This cavern was Princess Luna's personal sanctuary.

Sometime after her return from banishment as Nightmare Moon, she cast a location spell towards the mountain upon which Canterlot is situated. The spell led her down the mountain, into this hidden cave. No one else but her knew of this quiet cave, not even her older sister (especially since she is asleep right now).

High time she went here before her dream-walking duties. People wouldn't dream until they were well into their sleep anyway.

As of right now, the night princess is sitting on the edge of the water. The chill of nighttime made itself felt on her back, and her lower legs were immersed in the cool, clear waters.Luna dipped her hand in the water and dragged it across the surface, creating a small wake that traveled a good ten feet or so.
It's nearly time- she thought, as she sat on the edge of the clear water, illuminated by her moonlight and shining through the gaps in the cave. She took in more of the fresh cave air, relaxing as she felt the oxygen soothe her lungs.

Finally, it's time. Luna rose from where she sat, turned around and walked a short distance away, taking with her a black diving mask with blue straps and a pair of black fins with a blue stripe running through the middle. She returned to where she sat moments ago, legs hanging in the water again.

She adjusted the wide straps on her dark blue fast-back one-piece swimsuit and adjusted her hair, letting it free-fall to her back right side. Putting her fins to her left side, she decided to wear the mask first.

She spat on her mask, rubbing the saliva around the glass with her fingers before dipping it in the cave water and let them dry, before she put them over her eyes, securing the strap at the back of her head.

She took one of her fins and took her left leg out of the water, fitting her left leg in before she secured the strap around her ankle, giving it a tight enough fit that it would stay on. She then let her left leg back into the water before wearing the other fin on her right leg.

She stared down into the deep, clear water, illuminated by her moonlight, taking a deep breath and letting it out slowly. Luna felt her stomach rise and sink with her ribs, feeling as if the world was slowing down, moving with the rhythm of her heart. She took in a few more gulpfuls of air, feeling her stomach and the world around her move in rhythm with her breathing. When her lungs were full of air, she forced down several more gulps before pushing herself over the edge.

The water enveloped every part of her, the cool temperature soothing her exposed skin and every part of her body, even those covered by her swimsuit. Looking down into the dark, she dove down and swam towards the cave bottom. Swimming deeper, a pressure made itself felt in Luna's ears. The princess responded by pinching her nose and exhaling softly. Her ears squeaked and the pressure disappeared.

When she swam deep enough for the light to dim out, she stopped descending and twisted around, looking at the water surface. The moonlight cast itself into rays beneath the water surface, with everything around the patches pitch black in color. She turned around again, to face the dark bottom of the cavern pool.

Luna truly had the tranquility of the cave pool to herself. No one was there to disturb her, just Luna herself and the cool waters soothing her body and putting her in a relaxed state of mind. She began to swim around peacefully, going up, down, left, right and in circles, letting the water rush past her swimsuit and skin.

On occasion, she would extend her hands towards the surface to swim up, and a second later made a U-turn and swim down again. She would also swim in a backflip-esque motion in the dark waters, and sometimes stopped moving altogether, floating in limbo inside the water. Luna played around the rays of moonlight, sometimes leaving their shine altogether into the dark parts of the water. The moon princess would even sometimes twist around with arms extended forward and legs locked together, barrel-rolling through the cool pool. She mixed up what she was doing in different directions and orientations.

Luna slowly felt a pressure rising in her lungs, her chest beginning to convulse as she spent more time beneath the surface. Deciding that this long spent breathless would have to do for now, she abandoned her tranquil, breath-holding escapade and turned herself upright, looking up to the water surface and extending her arms upwards as she swam

As she reached the surface, Luna gasped in a mouthful of the crisp air, slowly letting out the pressure inside her lungs, and her chest convulsions stopped as soon as she took in her third gulp of fresh cave air.

Swimming free-style towards the edge of the water, Luna turned around and raised herself out of the water. Her hair, diving mask, skin and swimsuit were wet from being wrapped around water, which quickly ran in small streams down towards the earth, soaking the spot where she stood.
Taking off her fins, she put them to her side and took off her mask as well.

As liberating and relaxing this personal sanctuary of hers was, it was high time she returned to the castle. Her dream-walking duties for the day would not wait. Once she was done with those, Luna is free to return here and swim again if she so desires. No one was awake during the night, and the court had not required her presence for quite a while.
But she did not wish to return today.

She stood up, mask and fins in tow on her right hand, and raised her left hand. Casting a teleportation spell, her body glowed in blue light, starting from her left hand. Soon, her entire body glowed blue, and after a short while, she disappeared with her fins and mask, leaving nothing but a calm, hidden sanctuary, in which the last traces of her presence were the slowly dying ripples before complete silence ruled over the cavern, moonlight illuminating the now-perfectly still water.

A sanctuary for the Night Princess, where she would liberate her mind and calm her senses, surrounded by moonlight and her sacred darkness, beneath the cool waters' surface.

Author's Note

If you wish to know what a fast-back one-piece looks like, Google it.

Anyways, hope you enjoy my first story.

A little shout out to a story named "Ice and Steam", which is what inspired me to write this story in the first place. Keep in mind that I love underwater-stories like these, so expect more of such types of stories in the future, with different characters for each one of them.