Author's Note: This story is a reply to a story called Where's the Pool? by pres1111. This story might make a bit more sense if you read that one first. It's all up to you. We're trying to explain why the Doctor can climb and River can fall into a pool while the TARDIS is on its side. This is my explanation. If you can come up with one, I'd love to hear it. Set between A Christmas Carol and The Impossible Astronaut, no spoilers. I hope you enjoy...

The swimming pool was one of the many mysteries of the TARDIS that Amy Pond was yet to solve. She'd been travelling with the Doctor for about ten months now, but she still hadn't worked out how the Doctor could have climbed out of it when the ship was on its side. When she was seven it hadn't really mattered to her, but now not knowing the answer it was beginning to annoy her. She decided that today was the day she finally found out the truth. Leaving Rory in the library, Amy went to search for the Doctor. The control room was the logical place to start, because he was always tinkering with the TARDIS. In fact he never stopped.

"Doctor!" she shouted into the seemingly empty room. When there was no reply, she tried again. "Doctor!"

"Under here, Pond!" came the Doctor's voice in reply. She followed the sound until she was in the Doctor's tinkering area below the console. He was on his swing, his goggles that always made Amy giggle sitting on his head like discarded sunglasses. He was concentrating on whatever it was that he was doing to the wires under the console, but it didn't mean he couldn't talk. "What's the matter, Amy?"

Amy braced herself. She had asked about the swimming pool several times before and every time the conversation ended with the Doctor shaking his fist at a random part of the room. "I was just wondering about the swimming pool, Doctor."

The Doctor continued his rewiring, sticking his tongue out in concentration. "What about it?"

"How does it work? I mean, when I was seven, you said you climbed out of the swimming pool. But that would mean the pool would have been in he wall because the TARDIS was on its side," Amy said.

"The TARDIS wasn't feeling the best at that moment. Her gravity was all over the place," explained the Doctor. The wire he was working on sparked in his face and he yelped. "Now, if you'll excuse me..."

Amy nodded and left him to his tinkering. That was the straightest answer she'd ever gotten out of him on the subject, and she wasn't about to jinx it. She decided there and then that she'd go exploring and find the elusive swimming pool. "I'm going exploring!" she called back to the Doctor, as she heard another spark and another yelp. "And put your goggles on!" she added. The last thing she heard before leaving the room was the Doctor groaning. Health and safety was not his strongest point.

The TARDIS corridors changed in layout almost every time Amy wandered them, so it never got boring. The main rooms the occupants used, however, stayed in roughly the same place. The swimming pool wasn't a regular room, although Amy wished it could be. She was a poor swimmer, but when it was for fun, she still enjoyed herself. And if she did find the swimming pool today – no, scratch that, she would find it today – she would take Rory there sometime for a bit of... fun.

With that happy thought, she turned a corner away from the familiar area of the TARDIS that she knew well, and into the unknown. She walked for what seemed like miles without a single door. This surprised her, as the Doctor was always going on and on about how many rooms the TARDIS had. This seemed to be an awful lot of wasted corridor. She turned another corner and came to an abrupt stop. The corridor came to a dead end just ahead of her, but there was a door. Unlike the sci-fi doors of most of the rooms, this was a dark mahogany door with a polished golden doorknob. Amy took a deep breath and walked forward.

Reaching for the doorknob carefully, she slowly opened the door. Amy gasped, letting go...

Then she screamed.

A very loud scream with a distinct Scottish tone to it broke the silence in the control room. The Doctor started, falling off his swing with a thump. He landed in a heap of goggles, wires and a sonic screwdriver. He got up quickly and brushed himself down. He threw is goggles to the floor in frustration and unwrapped the stray wire from around his leg, throwing it to the side. Then he remembered why he had fallen in the first place.

"Amy!" he called. There was no reply. Of course not, he told himself. The Doctor really hoped she hadn't found his mood room. The mood room was a new thing for this incarnation. When he found something he liked, he put some it in that room to cheer him up when he was feeling upset. He didn't need it very often, though, because he had Amy and Rory. The Doctor had been careful to keep such a room a close-guarded secret. If Amy saw the room and told River Song about those fezzes... He shook his head to clear the thought. It was too bad to even think about.

The Doctor set off at a jog towards his mood room, fearing the worst. He found the room and checked inside. To his relief, his mood room was intact. Fezzes of all colours and sizes lined the shelves in perfect rows. He checked the TARDIS blue fridge-freezer in one corner and was glad to see his supply of fish fingers and custard was safe as well. He really couldn't wait to add some more things to his mood room.

But it didn't explain why Amy had screamed. Where was she anyway?

The Doctor left the room, locking the door behind him, and set off at a trot in search of Amy. He kept going for several minutes before he was confronted with a dead end that he didn't know existed. There was a dark mahogany door in the middle of the wall with a really shiny golden doorknob. The Doctor inched forward and pressed his ear to the wood. His keen hearing could pick out the sound of splashing in water, and he thought he could smell chlorine. He heard a grunt that sounded like it came from Amy and opened the door.

The room inside would have made many a normal person faint. On the 'wall' opposite to him was a swimming pool, full to the brim with water and a very angry-looking Amy. She was clinging to the edge of the pool, unable to get a grip on the slippery white tiles that lined its edges. For some reason, there were no steps out of the water. The gravity in the room meant that the door was in the roof. Amy was stuck, and the Doctor had to help her, even though she hadn't noticed his presence yet.

He took a step forward, his grip still firmly on the doorknob. He had no idea what he was going to do.

Gravity, however, decided for him. His foot slipped and he ended up hanging from the door, the threat of falling into the pool from the roof not helping him calm down. He, naturally, panicked and reached out to place a second hand on the doorknob. The Doctor's knuckles were white from the effort of holding his entire body weight, and he really wished that he didn't eat so many fish fingers. He grunted involuntarily. Amy looked up and shrieked.

"Doctor! Hold on!" she shouted.

"I... I can't..." the Doctor managed. He lost his grip on the door.

Rory Williams woke up in the library with a start. The book he had been reading fell from his lap with a thud. As interesting as the 'Energies of the Solar System' was as a book, it didn't half put you to sleep. Rory looked down to the book from his chair and noticed a long dribble running the length of the front cover. Carefully, he got up and placed the book back on the shelf, making sure that he hid the drool from Amy's scrutiny and the Doctor's despair.

Rory thought he had heard a scream from deep within the TARDIS, but wasn't completely sure.

He was completely sure ten minutes later when he heard another scream while reading one of the Doctor's many Agatha Christie novels. Rory sighed and went in search of the very noisy person who could be in trouble.

He screamed and plummeted eight metres down and into the pool below. There was a massive splash, and Amy was almost swept away by the Doctor's tidal wave. The Doctor broke the surface, coughing and spluttering. He swam awkwardly over to Amy.

"Are you okay?" she asked him as he reached her, placing his hand on the edge of the pool for support.

"Yeah," he said quietly. He pushed his waterlogged hair away from his eyes with his hand. "Are you okay?" he asked a little louder.

"Yes, I'm okay. But I can't get out of this swimming pool," Amy replied.

"Here, I'll help you out." The Doctor reached his hands to Amy's sides and gave her an extra push as she pulled herself up by her hands. She got one knee onto the dry ground and hauled herself up. Then she turned around and gave the Doctor some help out too, hauling him up with both hands.

Once they were both safely on the white tiles, the Doctor took a moment to make sure she was okay. Her typically short skirt was soaking wet, as were the rest of her clothes. Amy's hair was a few shades darker and clinging to her clothes and face when it could. It kept falling over her face and she brushed it back again. They both crawled on all fours over to the wall and sat down with their backs leaning against it.

"Ow," said Amy as she sat down.

"What's wrong?" the Doctor asked, failing to hide the concern in his voice.

"Nothing," she said with a wave of her hand. "It's just that the fall into the pool hurt a little."

The Doctor smiled. "Tell me about it."

"Yeah, that's a good idea. You can tell me about this room. What is it? Why is the door in the roof? Why is the swimming pool on the wall?" Why..."

The Doctor cut her off. "Whoa there, Pond! Slow down. The TARDIS has artificial gravity. Usually, the gravity all over the ship stays orientated to the same point, namely, the floor. At least, I think so. I still haven't been to all of her new corridors yet. But as far as I know, anyway, the gravity should be the same in every room."

Amy nodded. "That still doesn't explain the whole swimming-pool-in-a-wall bit," she pointed out.

"Sometimes, however, the TARDIS likes to have some fun with her occupants. This is probably one of those times. In fact, I'm almost certain. Yes. Playing around with her gravity is probably very entertaining for her."

"You're telling me that a spaceship is playing a practical joke on me, aren't you?" Amy sounded like she didn't really believe it.

The Doctor addressed the room around them. "You know, it isn't actually that funny!" he shouted, jabbing an index finger at the ceiling for effect. A loud hum filled the room, which was the TARDIS's equivalent of laughing. Apparently, it was actually extremely funny. The Doctor pouted. Amy elbowed him and he turned his pouty face on her. She sighed.

"Doctor, how are we going to get out?" Amy asked, her hand waving around the room.

"Oh," the Doctor said, finally noticing what Amy already had. There were no more doors in sight except the one that was currently shut on the roof. And unreachable. "Maybe Rory can help us," the Doctor suggested.

Before Amy could reply, there was an almighty scream and a splash from the swimming pool in front of them. Rory's head broke the surface of the water with a gasp. He spotted Amy and the Doctor and swam over to the edge. The Doctor shuffled over to the edge and helped him out, and he joined Amy against the wall.

"Where are we?" Rory asked as the Doctor joined them again.

"TARDIS practical joke," Amy told Rory.

"Or an artificial gravity technical disturbance," the Doctor said, earning a scowl from Amy.

"So how do we get out?" asked Rory, noticing the lack of doors.

The Doctor noticed that Amy was beginning to shiver now that she was drying off. "Some towels would be nice," he told the room. Three towels appeared in front of them. "Thanks," he mumbled, passing one to Amy and another to Rory. He used his own to dry his hair so it went for really slick and wet to spiky and messy, making Amy giggle.

"This still doesn't solve the problem that we're stuck here, Doctor," Rory rather helpfully pointed out.

Then the Doctor had an idea. "Okay," the Doctor announced, clapping his hands together. "Very good, Se..." he trailed off when he remembered his wasn't alone with his time machine this time, and so he really shouldn't use her name, "...TARDIS. It was a very nice joke. I'm in stitches, really. Aren't I Rory?"

"What?"

The Doctor sighed and whispered into Rory's ear. "I want her to think that I'm flattered that she threw us all into the swimming pool, but it we would all be much happier if she let us out now. Go along with it. And tell Amy the same thing." Rory nodded and leaned over to relay the message to Amy.

"Thanks for the dip, TARDIS!" Amy shouted to the room.

"It was great," Rory added, somewhat meekly.

The Doctor, Amy and Rory sighed with relief when a grey door appeared on the wall nearest the Doctor. The Doctor got up, setting his towel down. Amy and Rory made to get up as well, but the Doctor put a palm up to stop them. "It might be another practical joke," he explained, "so wait here."

He continued on his way to the door. It was one of the TARDIS's automatic doors which slid open when someone came close enough. The same happened on this occasion, but instead of salvation, a huge tidal wave of water washed him off his feet. The Doctor's arms flailed madly, trying to find something to hold on to, but of course there wasn't anything he could do to stop himself falling backwards into the pool. He coughed and spluttered as he swam over to the edge of the pool again, and this time both Amy and Rory helped him out onto the tiles.

"I must have left the shower on last time I was in there," the Doctor spluttered.

"Why is the TARDIS doing this to us?" Amy asked the Doctor desperately. He sighed. Had he not already explained?

"For fun." In reply, the TARDIS's hum of laughter filled the room. In the blink of an eye, the mahogany door that was once on the roof had moved to the wall beside Amy. Cautiously, she turned the golden doorknob. Thankfully she wasn't swept away by a huge tidal wave like the Doctor had been, and she stepped out into the grey-walled corridor that she had been exploring in about twenty minutes earlier.

"It's the way out!" she called. Rory and the Doctor all but ran for the door, and the Doctor stroked the TARDIS corridor walls.

Exhausted, Amy and Rory went off to have a shower together, with Amy vowing never to go exploring on her own again, leaving the Doctor with the problem of what to do with the swimming pool. He couldn't trust the TARDIS not to mess around with the gravity in it again, but he did think that it could come in handy some day. River was always jumping out of spaceships – it would be a softer landing than on top of him. He walked back to the control room, leaving a trail of miniature puddles behind him. He made a sticky note with blue marker pen and went back to the swimming pool, sticking the note on the door, which read:

WARNING: TOWEL REQUIRED AHEAD

Satisfied, the Doctor made his way back to the control room again. He had some tinkering to do.

A/N: Thanks for reading. A free virtual towel for every reviewer. :)