How long am I going to have to carry this thing around for?

It was still a decent distance from the settlement to the lake in question, and Sara had to cover that distance carrying all the equipment she'd been allowed/forced to borrow. Chester was on his usual perching spot on Sara's shoulder, looking at the bag she held it all in as he gnawed on a chestnut.

Lemme get this straight - you can breathe underwater with this?

He pinched his nose and lowered his head to simulate diving, keeping it there to represent staying under. Sara nodded in reply.

"That's pretty much it. There's enough air in that tank to let me breathe for at least an hour, which'll be plenty of time."

Chester, confused, jumped into the bag and started rummaging around the contents. He sat in one of the fins, finding it surprisingly snug though perhaps a little too big for a squirrel of his size. He shrugged at Sara from inside the bag.

What do these things do?

"Apparently they let me kick through the water easier when I wear them on my feet. They're meant to look like a fish's fins except, well, white."

Chester scratched his head. All this new-fangled human technology wasn't really something he'd ever studied before, so all of this at once gave him a sizable brainache. He poked his head out to make one last request, pointing back into the bag.

Uh...can I stay in here for a while? Things can't eat what they can't see, right?

Sara chuckled. Chester was afraid of some beast pouncing on him and swallowing him in one gulp, so he took every chance he could get to hide himself. She gave him a thumbs up, watching as he sighed with relief and put himself back snugly in one of the fins. He could sleep in this if he had the chance, but Sara's rocking would keep him awake for sure. She looked down at him, slightly confused by the sight.

I don't think anyone ever planed for fins to be used like that, but it works, I...guess.

The trip felt longer than normal, but maybe that was because Sara was hauling around the tank. It was noon by the time she arrived at the lake fully prepared, letting Chester out as she quickly changed into her gear. She very quickly switched into her bikini (hoping no-one was watching for the brief moments she was uncovered) and pulled the fins around her feet. There was a belt around the tank which she strapped around her waist, and the mouthpiece (apparently they called it a regulator) was hanging just under her chin, ready to put into her mouth whenever necessary.

"Be honest with me. Do I look silly?"

Chester didn't need to answer. He was lying on his back, giggling like a moron at the sight of her plodding around in the fins. He'd never seen a penguin before, but if he had he'd be able to say that Sara was waddling like one. She pouted, sitting on the edge and letting her feet dip into the water. Already the fins were becoming more flexible, making fluid swinging motions beneath the surface. She placed the regulator in her mouth, hearing it hiss as she breathed in and out. She gave the still guffawing Chester one last thumbs-up before falling forward and disappearing beneath the waves.

---

The first thing that surprised her was how many bubbles there were. Now that she could breathe as much as she wanted, she was letting off air all over the place. Mentally she found it difficult to get around the idea that such a small tank could hold so much oxygen. She'd read about the whole compression decompression thing, but it was still a hard concept to fathom.

Next, she started kicking, and amazed herself with the speed she'd suddenly gained. It was like having two tiny tails attached to your feet, and it was incredibly satisfying to cut through the water with a newfound power. It felt more fluid, more natural, and as she swam next to a school Sara found it easy to imagine herself as part of the group.

Knocking herself out of her daydreams, Sara scanned the depths to look for Dollie. She caught her looking awkwardly into the cavern, sadness filling her typically bright eyes. She slowed her kicking, hoping to catch her friend by surprise and give her a friendly pounce.

Despite her best efforts, Dollie perked up and turned around. She seemed surprised to see Sara, looking at her like some sort of alien initially. She became quickly aware that Dollie had probably been warned by the loud gurgling noises the tank was giving off, and facepalmed as she realised her own mistake.

S...Sara? What are you wearing?

Dollie pointed at Sara's mouth nervously with one fin. Obviously she was referring to the regulator, so Sara passed the message on as best as she could, by making exaggerated breathing motions and giving a thumbs-up. Dollie watched the bubbles cautiously for the first few breaths, but soon she gained confidence in the point that Sara was trying to get across.

But...what about your feet?

Dollie approached, poking Sara's foot since she couldn't think of any way for it to be giving her air. Sara peeled the fin back, proving that her foot was still there, and did a quick backflip in the water to show it had made her more versatile. Dollie gave her a quick clap, impressed by Sara's newfound grace.

"So, where were we?"

Sara pointed down the entrance to the cavern, watching Dollie's eyes brighten immediately. She nodded, and the two began to make their way through the tunnel. There was silence for most of the trip, broken only by Sara's gurgling, but clearly Dollie was pleased to finally be able to lead her friend down here.

The light started to fade the further in Sara went, and for a while she expected it to black out entirely, but from the other end of the tunnel another faint light was present. There was no obvious source, and Sara didn't expect the tunnel to break the surface again, so what else could it possibly be?

The trip was faster that either of them expected it to be, as the tunnel came to an abrupt halt. Sara, unsure where she was meant to go, looked around in all directions for a sign of where to go next but saw nothing on either side of her. That only left upwards, and it wasn't like there'd be anything-

"B-blub?!"

The ceiling suddenly came apart at one point, and the water continued upward for only a few more feet. Sara gurgled out a cry of 'huh?' at the sight - they were too deep for that to be the surface, so it had to be another cave. Curious, she swam through the gap and surfaced, wondering where she'd managed to wind up. She spat out the regulator almost instantly, already sick of the processed air - it felt putrid compared to the pure Yuriba air she was used to. Grabbing a nearby ledge, she hauled herself out of the water and onto dry land. Dollie popped up shortly afterwards, obviously not able to continue on.

So this is why she wanted me to see this - she can't find out herself.

It was a single intermittent air pocket, with another pool of water a few feet away. Dollie obviously couldn't make the transfer, so Sara would have to leave her behind here. Walking over to the hole and sitting at the edge, Sara looked towards her dolphin friend.

"Guess I'm on my own here on in, huh? Don't worry, I'll bring back anything cool I find. Wait for me, okay?"

Dollie nodded, and Sara gave her one last thumbs-up before dipping back into the water. The air in the cave had only been slightly better than that from the tank, but it still felt like fake air compared to what she was used to.

The second tunnel was noticably thinner - if Dollie were still following they'd need to go single-file from here. Sara continued on, hoping that it would open up soon - she was comfortable in these closed spaces, feeling too crammed up and stuck in place. Much to her relief, it did, with the faint light getting brighter the further in she went.

The tunnel expanded quickly, ending in a sizable clearing with a strange orb on the ceiling which seemed to be responsible for the light Sara had seen. It was obviously magical, but Sara was more intruiged by what was on the ground beneath it - a small, rural cottage, seemingly unused for some time. Despite being underwater it maintained an idealistic, perfect structure like it had come out of a book of architecture, and the front door hung open as if to invite Sara in. She didn't refuse - there had to be something interesting to see in here, surely.

"!?"

Entering the main hallway, Sara suddenly realised she was walking instead of swimming. It was as if gravity had restored itself to surface level, and suddenly swimming became next to impossible. Her bubbles still floated upwards, but nothing else followed suit. Looking around her, Sara noticed that the rest of the room seemed to work off the same principle - chairs, tables and shelves all acted like they were in an ordinary cottage above the surface, even though they obviously weren't. Sara was hardly an experienced magician, but she knew that this was some complicated magic at work.

Walking into the next rooms despite the fins' best efforts to stop her, Sara found a kitchen fully functioning and powered electrically (it even had an oven that worked perfectly!), a child's bedroom that hadn't been disturbed in some time with impossibly well-preserved books strewn around (all in some complicated, obscure language that she couldn't read) and a bathroom which by all logical thought processes shouldn't have been possible (a toilet that she could flush? How the heck did that work?). The house had been designed to work exactly like a normal house would, except without the whole 'air' issue. She had no idea how this place had come about, who'd built it or who it was intended for, and she hedged all her bets on the last room giving her the answers.

What welcomed her when she opened this last door was a sea of books, full to bursting - and the instant the door's support was removed, they all came crashing down.

"Mmph!?"

Shielding herself, Sara felt the books collapse across her, pushing her to the floor. To an onlooker it'd simply look like a pile of books had been left strewn along the floor, except that a stream of bubbles was coming out of something in the middle. Recovering from the mild bruising she'd managed to give herself she pulled herself out of the wreck, noting that on the way down one book had managed to fall right on top of her horn.

Uh-oh...I hope this isn't expensive...

Pulling it off her head, Sara took a moment to examine it. It was a diary, but there was a gaping hole in the book where the writer's name would have been. Logically it would've been more morally correct to leave the diary and be on her way, but Sara was too curious. If this thing had a clue as to who lived here, it was worth reading. Pulling the book open, she skimmed through the diary's contents, trying to understand the excerpts that hadn't been impaled.

It was a pleasant surprise to find that she could actually read this book unlike the others - maybe they'd been scholarly, complicated books or something. It was the sort of diary a young girl would keep, but the writer never mentioned her name - it HAD admittedly been on the cover, so mentioning it again would be unnecessary. Written here were stories of all the cool spells she'd learned during whatever day the excerpt came from, along with the occasional note along the lines of 'Papa will be so proud of me!'

One day's note seemed particularly interesting - at least, what she could make out of it:

Dear Diary,
Papa showed me how to get to this weird place today. He told me that it's meant to act like the house of an air-breather and I can use it if I want to take a break from studying, but I don't get how it works - why can't I swim around properly? Are air-breathers all really heavy?
There are lots of strange gadgets in here I don't understand, either. There's a thing called a 'my crow wave' which apparently makes things hot, but there's no sign of a crow anywhere. Did Papa forget to give one to me or something?
I know I should be finding out about these air-breathers, but I still spend a lot of the day reading about more new magic. If Papa thinks that I'm relaxing and then I come back knowing so many more difficult spells, he'll be really impressed! I taught myself to conjure food so I'm fine even without the my crow wave, and it's not like I'll ever live with the air-breathers anyway...it just seems like too scary an idea if I don't know anyone. Maybe if I met an air-breather who turned out to be really nice...

The excerpt cut off there, and skimming through further Sara realised it was the last in the book. She flipped through the pages, expecting nothing else from it, when a single piece of paper fell from the last few pages.

"Blub?"

Bending over to pick it up, Sara recognised it was a photograph. The subject was a young child with light pink hair and scarlet eyes, smiling widely at the viewer. It was a portrait shot, but from the fins behind her ears and the slits on her neck she clearly wasn't human.

A mermaid?

On the back of the photo the girl had written one last note - "Trying out this new preservation magic Papa told me about - a faux toe, he called it. All these air-breather inventions have really silly names."

Sara's eyes caught her air gauge as she turned away from the photo - from what she'd been told by the woman at the dive shop she had maybe fifteen minutes worth of air left. Time to get moving.

Maybe I should hold onto this photo...it's kinda the only proof I'll have that someone was living here.

Walking back down the hallway, and hoping that no-one would return to this place and discover the mess she'd made, Sara opened the door and jumped back into the clearing. She was swimming again the instant she cleared the doorway, and backtracked through the tunnel back to the air pocket. Dollie was waiting for her when she surfaced, eager to her what she'd uncovered.

Welcome back! Find anything interesting?

Dollie held her fins out, as if to receive something. Spitting out the regulator, Sara smiled at the question. What she'd found would bowl Dollie over no problem.

"I sure did. You're never gonna believe this, but there was a mermaid living down there."

Dollie's eyes widened. She waited for Sara to tell her what the mermaid had been like.

"Well, I didn't actually meet her...she'd been there for a while, but she isn't living there now. And her house looked just like one of the ones we have at home, and..."

As Sara continued on, Dollie's shock began to falter and was replaced with an unimpressed expression. She'd seen no-one, and apparently there was just a normal house down there. Why was she so sure there was a mermaid?

"...You don't believe me, do you? Well, that's why I brought back THIS!"

Sara flung the photo in Dollie's face, waiting for the criticism to fade from the dolphin's eyes. Against her expectations, it only grew more intense.

"What? How can you not believe this photo? Can't you see the-"

Looking back at the photo as if to confirm it, Sara cut herself off. The photo had faded away entirely - she was holding a simple white slip. Dollie's expression changed to a more understanding one.

It's okay, Sara. You don't need to act like there was anything great down there if there wasn't.

She shrugged (not very easy for a dolphin) and dipped under the water to return to the lake. For a moment Sara tried to stutter a defense - "No, really! I'm serious! I have the bruises to prove it!" - but even if Dollie was listening there was no way she would listen. Hauling herself over to the other pool, Sara dove down and followed suit.

Well, at least I know for sure what I saw, right?

---

"Sorry again about today, Dollie."

She'd never enjoyed breathing this much in her whole life. The air out of the tank was toxic compared to this, and that alone was enough to convince her to keep to freediving if she ever did anything like this again. Dollie looked up at her from the side of the lake, smiling.

It's fine. I would've spent all my time worrying what was down there if you hadn't looked for me. Thanks again!

She winked at Sara, content, before dipping back beneath the water. Sara had already unstrapped the tank and fins, grabbing the towel from her bag and giving herself a quick drying. A tiny head poked its way out of the bag, looking towards the discarded fins.

"Um...Chester, what're you doing?"

The squirrel darted from the bag to return to his resting spot. Sliding into one of the fins in a single, sleek movement, he was relaxed for about half a second.

After that he started realising just how cold it was.

"Eek!"

He was out of the fin as fast as he'd got in, shivering as he tried to shake the water out of his fur. Sara couldn't help but laugh.

"Aw, I thought you didn't like getting wet?"

Chester looked up, trying to cover his embarrassment by looking angry. It failed miserably. Still cold, he pulled himself onto Sara's shoulder after she finished changing. He pointed down and shrugged, asking Sara a question as she started the walk home.

So did you find anything down there?

Sara grinned, telling she was going to enjoy this trip back home.

"Depends on whether or not you're willing to believe me."