Desmond stared ahead, his eyes following the massive shape emerging slowly from the lake's depths, immersing him in its shadow. All around him the water hummed, as though a gigantic, invisible heart were drumming beneath the surface, its resounding palpitations reverberating across the beach. Fish were flickering wildly below, darting away. Desmond could hear their shrill voices, positively screaming in terror as they moved, pooling into the far reaches of the lake. A chill ran from the water up his spine, like cold hands running over his back. There was an urgency to the touch; he could practically hear the water whispering: "Run!"

But he couldn't. Feeling had abandoned him, and he simply floated there, paralyzed by terror, in the water. The roiling expanse that had once been his refuge was now his prison. The creature before him had risen to its full and incredible height, Mrs. Hathaway perched on top of its head, with her arms folded to her body in that characteristic way of hers.

"You ran away before I could talk to you," she pouted. "Didn't you see me approaching you, hear me calling you back when you rushed out?"

"Er . . . sorry?" Desmond squeaked.

"It took me so long to find you," she said in a bored voice. "You have no idea how frustrating it was, when I showed up at your house earlier and you weren't there. Fortunately, your neighbours are quite the gum-flappers. 'Looking for the Brookes's, are you?' they asked me. 'Gone on vacation for the holidays.' I didn't even have to ask! They just told me!

"Unfortunately, they couldn't tell me where exactly. So I had to check today's flights on my own. Boring, tedious work, checking the records, following your trail across the state. But I finally found you! And now, Desmond, I'm going to need you to come with me."

His heart began to pound more furiously against his chest. "Go with you? For what?" Surely she wasn't going to try to give him detention during the holidays? Was she going to feed him to the serpent creature? But if that was all, why had she gone to so much trouble to find him?

"Oh, now you want to hear what I've got to say? Unfortunately for you, that ship has sailed, dear. You will be coming with me, willingly or otherwise. Shakar!"

The last word issued as a strange, rasping screech, yet Desmond understood what she had said just fine: "Attack!"

The sea serpent's head swooped, plunging towards him, its horrid snout opened wide. Desmond instinctively threw up his arms to defend himself, forgetting that he was still holding his surfboard. The creature's fangs sank into the wood with several dull thuds. Desmond let out a yell of fright as it prised its teeth free from the board, splintering it, and swooped again. He did the only thing that seemed natural: he dove.

He sank into the gloom, forging downwards as the creature's massive head skimmed across the surface above. He could hear Mrs. Hathaway shrieking, "Under! He went under, you stupid beast!"

Desmond glanced up and saw the thing's huge shadow turn, then a second later its head burst into the water. Its body followed, and it plunged after him, those horrible eyes shining through the water like searchlights. But Desmond veered for land — land. . . . How odd it was that only hours before he couldn't wait to leave the bounds of the earth, and now his only chance of escape, perhaps even survival, lay in him reaching it.

But the creature was in its element, able to move much faster under the water than above the surface. Its large forelegs worked furiously on either side of it, propelling it through the water, its fangs bared as it advanced upon him.

Desmond kicked harder against the rolling sheets of icy water, but it was no use. No matter how good of a swimmer he was, this monster was much larger, much faster, and clearly adapted to sea life. He stood no chance. He found himself praying for something, anything, to hear him, to help him. But nothing came. The monster closed the distance and snapped at his leg, hooking him by the ankle between its huge jagged fangs, and it veered upwards, pulling him towards the surface. He yelled out in anguish, but nothing happened. It was over . . .

At that precise moment, however, a strange noise exploded in his mind: it was an odd, chittering sound, like the sound dolphins made, but low and guttural rather than high-pitched, and, most strangely of all, he understood it: "There!"

Hanging upsidedown by his ankle, bouncing around in the rippling tide, he struggled at first to make out what was happening below. Squinting into the gloom he saw, to his astonishment, what looked like a chariot racing towards him, pulled by several large, black, winged creatures that he recognized as manta rays. On either side of the chariot was a man, dressed in the most peculiar set of armour that he had ever seen, with skin that looked blue in the dim light, and legs that worked quite oddly as they swam up from the deep. Desmond wondered for a moment what was happening, where this chariot had come from, who the men were, but the creature holding him suddenly stopped, snarling at them, and he forgot his curiosity: all that mattered was that help had come, however it did.

The men detached themselves from the chariot and glided upwards, towards the serpent. It released Desmond and turned, hissing, to face them: a bright green liquid flew from its snout, spreading across the water as Desmond struggled to right himself, to evade.

One of the men pulled back, withdrawing from the pocket of his armour a large black bottle, which he tossed at the oncoming stream of fizzling fluid. The bottle exploded, releasing a burst of a bright, blue-and-purple substance, that looked oddly like fire. The temperature of the water dropped dramatically as the blast spread out, its force dispelling the liquid, which Desmond assumed was some kind of poison. As the sudden flare died away, another of the men erupted upstream, clutching a spear whose tip looked suspiciously as though it was comprised of a crab's claws.

The serpent fired more jets of poison, but the man wove around them all with incredible speed, ducked underneath the creature's head as it lunged, and thrust the spear into one of the creature's large, round eyes, which popped like an over-filled balloon. The monster screeched, thrashing around in agony.

Then the second man appeared beside him and, holding a kind of wooden contraption at his lips, fired a volley of what looked like spit darts, which sank into the creature's scaly skin. Within seconds it had stopped wailing, and began to sink silently into the depths of the lake and out of sight.

The first of the men swam upwards and broke the surface; he stayed there for a few seconds, then returned, shaking his head. "The other is gone."

Desmond watched in amazement, but gulped as the two men turned their faces towards him. The only one who had remained in the carriage, who looked much younger than the others, now exited and came swimming up towards him. He halted right in front of Desmond, gaping at him, and Desmond stared right back, his mouth hanging open in shock.

The new arrival was quite young, about the same age as he was, and humanoid in appearance. But his skin was sapphire. His eyes had no whites, they were mere almond-shaped sockets filled with a liquid-looking blackess, like ink-coloured jelly. He had no eyebrows either, and no nose; on either side of his rather thick neck were a set of large, elaborate slits, that Desmond recognized as gills. His seaweed-coloured hair was tucked neatly under a small crown, and his clothes, lurid shades of blue and purple, were bedecked with strange-looking pieces of jewellery, fashioned from seashells and shards of lapis lazuli. But his strangest feature, by far, was the massive silver fish tail that extended from his torso, where his legs should have been.

"Prince Arrluk," one of the men said, and Desmond jerked out of his reverie and looked around at them; they too, he saw, had similar anatomical compositions, which explained their odd, jerky movements through the water, except their tails were yellow and grey. He swam forward, but halted a short distance away, his head bowed. "My Lord, I know it is not my place to speak, but I would advise you to hold distance. He may be dangerous."

At the worst possible moment, Desmond found his voice again.

"Dangerous? Me? Dangerous? You just killed that — that thing — in like, two seconds! And I'm dangerous?"

The fish-man straightened up, looking, like his partner, taken aback. The supposed "Prince," however, was gazing at Desmond with fascination.

"You understood him?"

"Of course I did, why wouldn't I?"

"So you speak it?" the Prince said eagerly.

"Speak what?"

The Prince made a horrible, gurgling, choking sound. "The ancient language of our people — the Tethyians!"

"Um, I'm sorry, but I have no idea what" — Desmond tried to reproduce the awful hacking noise he had heard, which made him sound as though something was lodged in his throat — "is."

"But you just spoke it!" the Prince said accusingly, pointing at him.

"No, I spoke English."

"What is this — Eengleesh?"

"English!" Desmond said. "And that's my language, what you're talking in right now!"

The Prince looked confused. "I do not follow."

"Neither do I," Desmond said. He almost heaved a sigh, wondering what he had gotten himself into, then recalled with awful abruptness that he had been underwater for several long minutes. He began to writhe around in a panic, clutching his throat.

"What are you doing?"

"Can't breathe underwater — I'm drowning — help!"

"But you were breathing fine until now," the Prince observed, watching him curiously.

Desmond paused, realizing that was true. "Oh . . . right," he muttered, a little embarrassed. There was an awkward silence.

"I imagine we got off on the wrong — er — toe?" the Prince said. "Is that it? No, feet. Yes, we got off on the wrong feet, as humans say. My apologies for alarming you, but I believe you are the one I seek, erm —?" He shot Desmond a questioning look.

"Desmond," he said, holding out his hand without conscious thought. The Prince extended his own, as though he was going to shake, then raked his claw-like nails across Desmond's palm and withdrew his hand, smiling. "Ooh-kay," Desmond muttered, dropping his own arm and trying not to think how uncomfortable this whole situation was.

"I am Arrluk, Prince of Tethyia," said the other. "The world that exists below the suface of the water, deep within the seas, away from your — E-arth, was it?"

"It's actually pronounced urth. But, um, we're gonna have to get back to that. What do you mean, 'world within the seas'? There is no world down here, apart from all the fish and weird plants and stuff."

"Is that so?" Arrluk said, sounding amused. "Very well then, allow me to prove you wrong." He gestured at his carriage.

"Prince Arrluk!" one of the guards burst out, as though he could no longer contain himself. "Please —"

Arrluk ignored him. "It's settled, then? You will be the first of your kind to visit the world hidden in the depths, and I will explain to you why I came to find you along the way. You will need to come with us anyway, there is no antidote for a hydra bite on your world, to my knowledge." He pointed at Desmond's leg, where several deep gouges stood out on the skin, oozing green slime. He had not even noticed.

The rational part of his brain told him that this was crazy, that he should refuse, but his eyes quickly silenced that area, reminding it that logic had no place in this scene of poisonous sea monsters, English-speaking mermen, and strange worlds below the waters, that they were presently observing. He shrugged; he was already quite deep in this whole mess — What the hell?

He agreed to go.

Arrluk directed him to the chariot where, furling in his tail, he sat down and beckoned Desmond beside him. He took his seat beside the Prince, and the guards took their places at the sides while the fourth merman, the carriage's rider, secured the thick, seaweed reins. And they dove. The manta rays hurtled ever lower, pulling them deeper and deeper. Bubbles rushed past them as they went, the area becoming colder and darker, so that Desmond started having trouble seeing.

But then, without warning, the whole area was suddenly illuminated by a blazing blue light, the sudden brightness searing his retinas. Blinking rapidly to adjust to the glare, his jaw dropped as his eyes fixed upon the source.

A spiraling ring of blue fire was swirling below, the sapphire flames igniting the gloom. The flames encircled a large, flattish hoop of ice, crystal clear and glassy smooth, but which showed no reflections. It was like some kind of portal. They were moving closer and closer towards it, passing huge slabs of dark, glittering rocks. In some distant chamber of his brain, Desmond vaguely remembered something about pressure, going too deep into the sea and being crushed like a soda can. But again he dispelled the sudden feeling of disquiet, noting that he shouldn't have been able to breathe anyway.

The mantas hauled their chariot straight towards the ice mirror, then disappeared inside without leaving so much as a chink on the surface. The reins were still there, pulling them in. Desmond closed his eyes, expecting some kind of impact or discomfort. But none came. . . . On the other hand, the effect was rather like when he had first plunged into the lake above, a pleasant coolness running over his bare skin.

Darkness stretched on for a few seconds — then they burst out into waters brighter and bluer than even the portal-lit bottom of Lake Bozeman.

"Welcome to Tethyia," Arrluk said, smiling, his arms opened wide as he gestured at the scene unfolding before them.

Desmond leaned over the edge of the chariot and stared out, drinking in the sight. Below them, immense swathes of caves stretched on for miles and miles across the sea-floor, elaborate light grey tunnels arranged in shapes that resembled wasp hives, enclosed by an enormous, heavenly bubble that seemed to span the entire sea floor. Even from this height Desmond had no trouble making out the large farms of algae, coral, and other aquatic plants, some of which held grazing herds of manatees, small whales, and dolphins. A peculiar line of pipe-like structures ran throughout almost every cave, and Desmond could see hundreds of mermen, merwomen, and even merchildren bustling about, dressed in what looked like average wear for their species: dull, revealing garments that hung loosely around their skin, carrying out basic chores.

The caves sped past below them, and now Desmond turned his eyes on the sight ahead.

"The capital city," Arrluk said. "Kumari."

The capital looked more like something from the surface world than anything Desmond had seen of the sea so far. It was smaller than the caves, but the architecture was vastly superior, with intricate buildings of varying sizes and states of splendour: large, round-walled, and topped with dome-like roofs, yet with the same pipe-like structures running to each house, the houses were made of gleaming light blue coral, brightly painted stone, and, to his slight surprise, cement, with strange markings printed across the high doors.

The merpeople — or Tethyians, as Arrluk had called them — he could see here were dressed in robes of fine silk, dyed in vibrant colours — green, yellow, and white.

Desmond pried his eyes from the sight quite abruptly and turned instead to Arrluk. "I don't understand," he said. "How is this possible? How can there be a whole world under the seas? And one this advanced?"

"I suppose I should start with the basics," Arrluk said. "I've been doing some reading on human history, most of it is forbidden from being told here, and the parts that aren't are passed as fiction. My father — I will explain why later — allowed me a deeper look into his personal library recently, and I learned that, as you may well know, the discovery of fire basically kickstarted your world's development: allowing for the introduction of metallurgy, among others.

"Tethyians do not have access to fire, for obvious reasons. Instead, we have something more powerful, yet just as valuable . . . magic."

Desmond gaped at him.

"We don't need fire when he have resources such as magic, and, of course, natural marine composites."

"You mean like, hydrothermal vents?" Desmond asked, recalling Geography lessons of years before. "Natural metal deposits, gas stores?"

"Exactly. Along with everything else you've stated, we have other materials such as coral, ceramics, animal bones, stone, shells — you have no idea the kind of things that certain animals leave behind under the right conditions, and how we can harvest them." He leaned forward, pointing out of the chariot into the city below, and Desmond leaned forward too. Arrluk was pointing at the odd pipe-like lines, which were patterned differently now than back in the caves. "Crab and turtle shells, specially bred. Massive things. The shells are harvested when the animals die or create new ones, and one of their uses is the creation of our pipes, which are set up to transport water from the nearest natural vents to provide hot water when we need it.

"Basic Tethyian sorcery regulates heat levels, makes it less lethal to our kind — you should know that water is an incredible conductor of heat. We also possess stores of natural energy. You may have heard of these, in what your world regards as fiction. I believe they're called . . . Jino, what were they called?" he asked one of the men, the very same one who had protested to Arrluk's decision to bring Desmond with them.

"Leylines, my Lord," he said tonelessly.

"Yes, leylines. We also, apparently, took a leaf out of you surface-worlders' book, using waves to produce energy. And everything fell into place."

"Wait, hold up, you said you can't use fire down here, but then what was that blue thing you used earlier? Looked pretty much like fire to me."

"Hyrule, you mean? No, it's not fire. More like the opposite than anything. Fire creates and releases heat and light. Hyrule, while it does generate light, absorbs heat from its surroundings, to make itself hotter. That's how we regulate the hot water in our buildings, using Hyrule to siphon heat, make it cooler."

"Wow," Desmond murmured. "What else can you do?"

"Patience, Desmond. Let's take care of your leg first. Ah, here we are. Welcome to my home," he said, gesturing ahead. "The Palace of Kumari."