It had started with a mistake – The Doctor’s mistake. He had turned a dial on the TARDIS console further than he should and changed the destination by a hundred thousand light years.

Then he mistook the surface of the planet by five fathoms and the TARDIS materialised on the bed of an ocean.

“Oh dear me,” The Doctor opined.

“But it’s marvellous,” Zoë told him as she stood with Jamie at the open door with a force field holding back the water. They watched the fish swimming past them and appreciated how unique this perspective was. They were mostly the same as the fish on Earth except for their colours. There were bright reds and yellows as well as the browns and silvery grey that they expected, and they came in sizes from tiny, almost translucent shoals that flashed through the water to as big as a dolphin. Jamie was more interested in the middle sized fish, the sort that most closely resembled the trout and salmon that his people supplemented their diet with from the open lochs of the Scottish Highlands.

“There’s no shortage of food here,” he said. “Any people would be able to live well enough.”

“Are there any people on this planet?” Zoë asked The Doctor. “I mean, people, people, of course.”

The Doctor knew what she meant. Even though she worked on the Space Wheel, she had only ever come into contact with non-humans when they were threatening her – the Cybermen, the Ice Warriors, The Krotons. When she thought of ‘people’ she thought of those that looked like her – the Dulkis or the Gond. It wasn’t quite correct. ‘People’ could look different to humans, but Zoë wasn’t ready to accept that, yet.

Jamie was surprisingly more open-minded about it, considering that the most alien thing in his life before he joined the TARDIS crew had been English soldiers.

It was he who first spotted the ‘people’ who swam curiously towards the TARDIS, attracted, perhaps, by the warm light from the doorway. They were short, the males about Zoë’s height and the females coming up to her shoulder. They were all naked, so it was easy to tell which was which. They had webbed hands and feet and gills from which bubbles of air streamed as they swam close, their big eyes wide in astonishment and interest.

The first two, a male and female, passed through the forcefield and stood upright on the TARDIS floor as Jamie and Zoë stepped back to allow them entrance. They put down the spears with which they had protected themselves from the more predatory fish and dropped the still dripping nets full of crustaceans that they had gathered from the sea bed.

They were a pale blue colour and completely hairless in addition to their other attributes. They looked at Zoë with curiosity and reached towards her. She backed away nervously, but The Doctor calmly told her not to worry. The fact that they had put down their weapons proved that these people were making friendly contact.

“It’s her hair,” Jamie said. “They want to touch it.”

“They’ve never seen anything like it before,” The Doctor observed. Zoë laughed as the natives ran their hands through her shoulder length soft hair. It tickled a little. They laughed, too and the bond of friendship seemed to have been made.

“I’m Zoë,” she said to them. “This is The Doctor and Jamie.”

“Ido,” said the man. “This is Alo, my wife.”

The words he used were in his own language, but that had never mattered as long as she had travelled in the TARDIS. Zoë always understood the languages spoken by natives of different planets. She always meant to ask The Doctor about it, but they were usually too busy running from unspeakable horrors to worry about it.

“Do you live in the sea?” Zoë asked them.

“No, we live on it,” Ido answered. “Do you live in this box under water?”

“Not usually,” Jamie said. “The Doctor got his calculations wrong.”

“Come up,” Ido suggested. “Be our guests.”

“We should be honoured,” The Doctor told the natives on behalf of himself and his companions. Ido and Alo picked up their spears and nets and stepped back into the water where they were clearly as much at home as in air and swam up towards the surface. The Doctor set the TARDIS to find sea level and it, too, began to ascend.

The TARDIS emerged into a bright, sunny afternoon in the middle of a wide, blue ocean. There was no land to be seen in any direction but there was a small community of shelters built upon great rafts. Shelters and rafts alike were made of thickly woven layers of tough reeds seasoned with some kind of resin. People just like Ido and Alo sat on mats woven from the same reeds and cushions of a rough thread that might be the reeds spun thinly in some way.

Ido invited The Doctor and his companions to join his family on their raft. They stepped gingerly from the doorway of the TARDIS to the reed surface. They noticed that their hosts had put on loose shifts made of an even finer version of the cushion fabric.

“Please, sit,” he said. A boy came from the shelter with cushions for their guests and Alo brought large shells filled with a pale green liquid that tasted cool and fruity. The Doctor again thanked their hosts for their hospitality.

“This is our son, Dal,” Alo said about the boy who knelt beside Zoë and touched her hair enthusiastically. She took a comb from her pocket and showed him how it worked, and he sat contentedly combing her hair.

“Do you live on a raft all the time?” Jamie asked. “Where is the land?”

“Land?” Ido and Alo looked at each other and turned over the word.

“You mean islands of rock above the water?” Ido asked.

“Yes, I suppose I do,” Jamie considered.

“I have heard tales, myths, stories,” Ido said. “Of dry places with plants growing upon them. But I have never seen such a thing with my own eyes. I was born on the water. I expect to die upon it.”

“But that’s not possible,” Zoë said. “How can you possibly live your whole lives on the sea?”

“Why not?” Alo asked her. “We have all we need. There is food in the sea – all kinds. There are reeds to make our clothes and shelter and the raft beneath us. What other way should we want to live?”

“There are many ways to live,” Zoë told them gently. “I live and work in space – beyond the sky – in a huge wheel.”

The word ‘wheel’ was unknown to them, too, though they did seem to understand about space, about stars and planets beyond their own world and accepted that she came from there.

“My land – Scotland….” Jamie added. “We have moors that stretch as far as your horizon, wild grass, heather, where a man can walk for days – at least he could before the Sasanachs came and told him not to.”

“Walking for days on dry ground….” The concept was entirely alien to the raft people. Jamie tried in vain to describe Scottish heather and gorse and the pleasure of walking upon it. The closest Ido and Alo had to it was swimming along the sea bed hunting for the crustaceans that Alo was now preparing on a grill made of stones and dried reeds carefully built so as not to burn through the raft. She also appeared to be preparing a salad of green leaves and something that looked like tomatoes. Zoë asked where they came from.

“They grow on the sea bed,” Alo told her. “These are gumsa leaves, and sliced ripe canice fruits. They are very nutritious and can be used as a sweet or savoury dish.”

Sweet or savoury weren’t the tastes that were worrying Zoë. She was wondering if vegetables from the sea would taste too salty. When the evening meal was brought to the low rush-woven table where the family and guests gathered, though, she was pleasantly surprised. The canice had a cool, slightly sweet taste a little like tomatoes and weren’t salty at all. Neither were the crisp gumsa leaves. They were served with strips of flame grilled white fish that had a lemony flavour.

That was the starter followed by those baked crustaceans which were cracked open and eaten with the fingers. Finally there was a sweet pudding like a blancmange but far more colourful and flavoursome. There were jugs of partially fermented juice which was extracted, the visitors learnt, from the same reeds that yielded fibres for raft building and cloth weaving. Fresh shoots from the reed beds also made a delicious staple food.

“Everything they need comes from the sea,” Zoë said. “How wonderful.”

“There are feathers in this cushion,” Jamie pointed out. “They don’t come from the sea.”

“We catch birds in the air using nets,” Ido explained. “The feathers are used as well as the meat.”

“Where do the birds come from if there isn’t any land?” Jamie asked. “Where are their nests?”

But Ido and Alo couldn’t understand the question. As far as they knew, birds flew in the sky. They didn’t have nests.

“It can’t be right,” both Zoë and Jamie insisted. The Doctor said nothing. Perhaps he knew ways for birds to lay eggs in the air. He sat at the front of the raft – as far as a back or front could be determined, and held up his hand to measure the breeze and dipped it into the water to test the salinity and the strength of the current.

“Do you simply let the currents drive you?” he asked Ido after a while. “Or do you use oars or sails to change direction?”

“Mostly we let the currents take us along,” Ido answered. “But once a year it is different. When the wind blows cold and ice covers the waters, we go south following the red path of the moon to the warm horizon.”

“I see,” The Doctor said. He looked towards the southern horizon. Hanging in the blue sky was a large pale red moon – a twin planet in dual orbit, of course. At night when its reflected light was not competing with the sun itself, it would cast a long red highlight across the ocean – the red path. Ido seemed to be saying that the path coincided, at a crucial time of year, with a strong current that brought the rafts to a warmer part of their planet.

It struck him as a magnificent arrangement of nature and navigation.

“We shall turn the rafts into the path of the red moon in nine days,” Ido added. “At that time the current is strongest.”

“I should like to stay to see it,” Zoë said. “Doctor, do you think we could? We have nowhere special to go and this is a beautiful place to stay for a little while.”

“Aye, it would do me nicely for a while,” Jamie added. “I could do a bit of fishing. Makes a change from Cybermen.”

“I think a little holiday here would be very pleasant,” The Doctor concurred. Zoë smiled warmly at him. Jamie grinned. The Doctor had called it a holiday, and neither of them could think of a better place for one than here.

And it really was a delightful time. Zoë, born into a highly technological world with her gift for complicated maths and computer languages, found it utterly different and refreshing living among people who needed none of such things.

She took a keen interest in all of the daily work, fishing and gathering food from the sea bed, cooking, weaving mats and cloth, maintaining the shelter, and, most importantly, the raft itself.

nShe noticed that there were few strictly male or female jobs. Ido would sometimes cook, Alo would do the maintenance work. Both of them went fishing.

Jamie was in his element. This wasn’t the crofter country he knew, but it was a kind of subsistence life he was accustomed to. People who worked to eat and provide shelter for their families were his sort of people. He joined enthusiastically with the fishing. He had to wear scuba tanks and a wetsuit to join in fully with the underwater hunts, of course. Ido couldn’t help laughing at the sight of him dressed that way, but when Jamie speared enough fish for the evening meal he praised him fulsomely and accepted him as one of their hunters and gatherers.

The Doctor spent much of his time making calculations of the width and speed of the currents the raft travelled along. He studied the stars at night and the position of that red planetary moon in the sky.

As they travelled, they were joined by other rafts. The first two were owned by Ido’s brother and Alo’s cousin who came with their families to join the migration to the great red current. Later others joined them, friends that they saw at this time of year. There was news to catch up on, marriages and births to celebrate, deaths to mourn, betrothals to be made now that the whole loose community was gathered together.

And then they turned the rafts towards the southern horizon. It was very much a joint effort, with the rafts close together, the outer ones rowed by all of the strongest men and the fittest, youngest men and women. The Doctor and Jamie took their turns at the work. Zoë tried, too, but she found it difficult and made herself useful, instead, bringing a big jug of fruit juice around the rowers so that they could refresh themselves whenever they wanted.

Two days and nights of intense rowing brought them finally into the red path – the long reflection of the moon that stretched all the way to the horizon. The rowers could stop almost immediately. The current was so strong that everyone felt the difference.

“It’s amazing,” Zoë commented. “You would think the rafts had motor power. We’re going at a cracking pace.”

“Indeed,” The Doctor said. “At least seven knots, I should say. It’s a very impressive speed. Faster than the Gulf Stream in your Atlantic Ocean on Earth.”

“It must be created by the same forces,” Zoë posited. “A warm stream of water moving faster than the colder water around it.”

“Yes,” The Doctor agreed.

The raft dwellers themselves didn’t have any scientific theories. They just accepted that the current was there. Jamie wasn’t really interested in the discussion of warm and cold water densities that The Doctor and Zoë launched into. He was happy to lie down on the edge of one of the outer rafts and trail his hand in the fast flowing water. He wasn’t the only one relaxing. All those who had worked hard rowing were now enjoying the chance to rest.

“It looks so beautiful, doesn’t it,” Zoë said, when the scientific discussion had run its course. “It almost seems as if the water is running towards the moon. But, of course, that’s impossible. There are thousands of miles between the two bodies.”

“It is a charming visual effect,” The Doctor agreed. He, too, seemed content to enjoy the end result of all the labour. Zoë wondered how much longer the ‘holiday’ would last, though. The object had been to see the migration to the ‘red path’. Now they were here, she supposed they would leave, soon.

She felt a little sad about that. Even though this was so very different from the technological life she knew, she had grown to love it so much. She would miss the friendly raft people and their beautiful world.

But The Doctor didn’t seem in any hurry to leave. They spent another two glorious days travelling by the red current towards the endless horizon.

Then one night after they had settled down to sleep aboard Ido’s raft, Zoë was shaken awake by Jamie. The Doctor had told him to rouse her.

“There’s something wrong,” he said. “The Doctor said there’s danger ahead.”

“Danger? Here?” Zoë sat up at once. “But surely there’s nothing dangerous on this world. It’s a beautiful, peaceful place.”

But there was certainly something wrong. All around her were sound of consternation. The raft people were staring at the horizon and murmuring loudly. Some of them were grasping oars and trying to turn away from the current.

“We’re going too fast?”

“We’re going far too fast,” The Doctor confirmed. “At least forty-five knots.”

None of the raft people knew anything about knots. They just knew that they were travelling too fast. Zoë listened to their panicked voices. They were convinced that they were being pulled over the edge of their world.

“But that won’t happen,” she assured them. “Your world is round like any other. The current will surely slow down eventually and you’ll be safe.”

“No, they won’t,” Jamie contradicted her. “They’re going to die. Look at it.”

Zoë looked towards the horizon and remembered what she had said a few days before about it looking as if the ocean was running towards the red moon.

It wasn’t just a poetic idea now. The water really WAS being drawn up from the ocean and dragged towards the other planet. Something was doing it – something deliberate and mechanical, not a natural phenomenon.

“Doctor, what is it?” Zoë asked.

“I don’t know, but I intend to find out,” he answered. “Come along, my dear girl. Jamie, into the TARDIS.”

“You’re leaving us?” Ido looked concerned. “You would desert us in our time of despair?”

“No, oh no, my dear fellow,” The Doctor assured him. “We’re not deserting you. Not at all. Oh dear me, no. We’re going to try to find out what and who is responsible for this and to put a stop to it. Do what you can to move the rafts out of danger, meanwhile, and we will be back, I promise.”

He grasped Ido’s hands in his and held them for a long time before doing the same for Alo. That, and his words, reassured them both, and the same reassurance was passed on to the other raft people. The Doctor and his friends were going to rescue them from this danger that had come upon them.

“Close the door, Jamie,” he said as he came aboard the TARDIS. Jamie did so. The Doctor moved around the console, carefully checking instruments.

Zoë wondered for a moment if he WOULD be able to make good on that promise. The TARDIS was so very temperamental they might dematerialise and re-materialise a million light years away, never to return again. What a dreadful outcome that would be. Not only would they fail to help the raft people, but they would die feeling betrayed by The Doctor. That was the most terrible thing after he had promised to help them.

“There we are,” he said, much to her relief. “That’s the source of the trouble. A nasty sort of gravitation disrupter in the middle of the central desert. I’ll soon sort that out.”

“You can?” Zoë asked, perhaps sounding a bit TOO surprised. The Doctor looked quite aggrieved at her scepticism. “I mean, of course you can. But will it really be as easy as that?”

“Oh, indeed,” he assured her. “Gravity is the most natural force in the universe, you see. It’s why trees grow upwards and tides go in and out. It’s why planets go around suns and moons around planets and up is up and down is down. Anything that interferes with gravity is so completely UNnatural that putting a spanner in the works is a cinch.”

“Aye,” Jamie pointed out. “As long as they let you near the works with your spanner. There’ll be guards, surely?”

“That’s the chance we’ll have to take,” The Doctor conceded. He reached for the materialisation switch and the TARDIS made its familiar noise as it landed inside the gravitational disrupter.

After the simple, non-technological life of the raft people, seeing the huge mechanism enclosed in a great glass dome was rather breathtaking, but admiration of the workmanship was spoiled by the knowledge of what it was doing.

And the noise. The machine itself was near silent, but outside the dome water was crashing down, drawn through space by the powerful disrupter and pouring into the desert that was no longer entirely desert. A small lake was forming and part of the dome was underwater already.

“That explains WHY it’s happening,” The Doctor shouted above the noise of the pouring water. “Somebody is terraforming this planet using the resources of the other. But even so, it cannot be allowed. I must put a stop to it.”

With that, he began studying the complicated computer at the heart of the mechanism, murmuring to himself as he worked.

“Zoë, Jamie, come along and help here. I do not have the arms of a gorilla, and I need to turn three dials at once. Take those at either end, and when I tell you, turn smartly three quarters, you turn clockwise, Zoë, and you anti-clockwise, Jamie.”

Jamie looked at his hands and turned imaginary dials in order to remember which was anti-clockwise, then positioned himself at the array. Zoë had to pause for a moment, too. She had been educated using digital clocks and had only really got used to analogue dials since joining The Doctor, but she knew what to do all the same. Both companions waited for the signal before turning their dials. The Doctor turned the middle one before operating two levers at once.

At first there seemed no result of their action. But then, slowly, the noise lessened. The water stopped pouring down over the dome. The gravity disruption had stopped.

“We’ve done it?” Jamie asked. “It was really so easy? Just turning a little knob like that?”

“As easy as that. But there is nothing to stop anyone turning it back on again. Our work is not yet done.”

Zoë wondered what The Doctor meant at first, but it became quite obvious when two people materialised in the dome in a sudden shimmer of bright light. They were dressed as mechanics, and carried no weapons, but as soon as they saw The Doctor and his companions they accused them of being trespassers and threatened to arrest them.

“Arrest me?” Jamie responded angrily. He reached for his dirk and ran at the closest man who immediately put up his hands and surrendered. The other one did the same when he saw that Jamie was armed.

“I rather think it is you who are under arrest,” The Doctor said calmly, examining the logos on their overalls and the transmat controls on their wrists. “You belong to an organisation called ‘New Horizons’. What’s that when it’s at home, which it clearly isn’t if it is here.”

“Terraforming,” one of the men managed to explain. “We prepare planets for habitation. This one was designated uninhabitable because there was no water. We were….”

“Stealing the water from the other planet,” The Doctor finished. “So we saw,”

“It’s not stealing. The other planet is uninhabitable with nothing but water. Sharing the resource would make two planets fit for colonisation….”

“But it isn’t uninhabitable,” Zoë protested. “You got THAT all wrong, you silly people. You were about to do something absolutely terrible.”

“I think we need to see your superiors,” The Doctor said. “I do hope they are prepared to be reasonable. Zoë, Jamie, you hold onto that chap there. I’ll stick with this one. Now, take us to your leader.”

They materialised aboard what was clearly a space ship in orbit around the desert planet. A view from a huge exo-glass window showed the ocean covered one emerging as a rising moon above the wide plateau where the artificial dome was visible even from space. Their appearance caused consternation, especially when it was clear that the two mechanics were The Doctor’s prisoners, not the other way around.

“Under the terms of the Tiron Proclamation of Intergalactic Year 22698, you have committed a potential act of genocide which invalidates your contract to terraform the planet below,” The Doctor said with an authority in his voice that belied his hobo-like appearance. Zoë and Jamie had both seen it before, but the directors of New Horizons obviously hadn’t. They were hypnotised by the cyclone of rage that was vented upon them.

“Of course… if the ocean planet is inhabited that changes matters considerably,” the Director of the company admitted when he had chance to get a word in. “May I ask how many millions of people live on these rafts?”

“I don’t think there ARE millions,” Zoë said. “We’ve only met a few. But….”

“It does not matter if there are a million or six billion, or a hundred people there,” The Doctor said when the Director began to talk about transplanting the raft people. “It is their planet. There are a dozen more treaties I could name that guarantee the preservation of indigenous peoples and their ways of life. You will not touch them or one single drop of the water that covers their world.”

“Then what are we to do?” the Director questioned. “There are two hundred thousand colonists expecting to settle on the planet below. They are on their way in deep space cruisers.”

“They will have to turn back,” The Doctor insisted.

“Why isn’t there any water there?” Jamie asked. “It doesna make sense. There’s more than enough on the ocean planet. Why should that one have none?”

“It is in the same orbit,” Zoë added. “The same temperature. Jamie is right. It really doesn’t make sense.”

“You’re both right,” The Doctor told her. “Show me the geological reports for this planet.”

He addressed the last to the Director, who found the information he wanted without even questioning The Doctor’s authority to ask for it. He felt peculiarly powerless before the strangely dressed intruder who, deep down, he thought he ought to have thrown into his brig rather than co-operating with his demands.

“Ah, yes, I see,” The Doctor said after studying the geological report for a little while. “Yes, I see…. You didn’t really look at this properly, did you? You never even considered the water existing on the planet below.”

“There is no water on that planet,” the director protested. “It is a desert.”

“The water is underground,” The Doctor pointed out. “Look at the mineral content of the sand. It contains fossilised shells, traces of sodium. That desert below used to be an ocean bed. Some time in the distant past the water submerged, leaving a desert surface and huge oceans of water in caverns between impermeable layers of rock in the mantle of the planet.”

“You mean… there IS water there?” Zoë concluded before anyone from New Horizons had worked out what The Doctor was saying.

“There is MORE than enough water for irrigating fields, supplying settlements with potable drinking water, all that a new colony planet needs. And you have a machine down there in that dome that can make the job easy. All you have to do is reverse your gravity disrupter and it will bring the water up from beneath the surface and fill a freshwater lake the size of a… a very big lake. Anyway, it will work, and you can leave the other planet alone. It belongs to the raft people.”

Two nights later they sat on a gently drifting raft on a warm, balmy night and looked at the red moon. One huge part of it was no longer red – it was a green-blue colour. The gravity disrupter had already brought enough water from the subterranean oceans to create an inland sea. Soon, without even needing any kind of terraforming, rivers would form. The land would be watered. It would be fertile again, ready for those colonists who were going to come to live there.

“They won’t be allowed to interfere with this planet,” The Doctor said. “The raft people will continue to live their peaceful nomadic life upon their ocean. The new settlers will make what they choose of their new world, and it is to be hoped that they will be content there.”

Zoë looked up at the red moon that would, in time, no longer be red, but blue and white and green like the Earth she came from. She probably wouldn’t see it that way, but she and Jamie and The Doctor had begun the process that others would finish in time to come.

Meanwhile, The Doctor had promised another week of holiday with the raft people of Ocean Blue before they went on again to new adventures in the TARDIS.