Why can't Zuko & Katara navigate by the stars?

Long answer: will be mentioned later.

Short answer: even if they wanted to, they don't have so much as an oar. Much less sails or an engine. Navigation is impossible if you can't control your own movement. So the question is moot for now.

Notes: Okay, here's another part. This one might be a bit rougher because I didn't rewrite it as stringently as the other chapters. I've had several scenes written ahead of time (some posted to livejournal), but I've been fleshing them out for posting here. This scene was already description-heavy rather than dialogue-heavy, though, and I only felt like adding a few bits and a paragraph here and there.

Warning: I have zero medical expertise. None. Don't even try to apply scientific knowledge to what you're about to read. Just go with it. Like movie!science. It doesn't have to make sense, it just has to fit with the plot.

Act 1

The Sea

Scene 4

He hadn't told her about the wound.

On the sixth day she woke to find Zuko shivering on the floor of the raft, covered in sweat. The sight hit Katara like a punch to the chest: wrong wrong wrong. The night before he'd been fine, complaining of a headache and hunger and thirst, but otherwise fine. She'd been feeling all those as well: the sun cooked them in the day; the breezes chiled them at night; the water was close to being gone. But they'd both been okay: bickering and hoping for rescue just like all the other days.

At least... she'd believed him to be okay. Now something was horribly wrong and she didn't know what had changed. He'd argued with her less, but Katara thought he was finally tired like herself. She'd thought... Surely there would have been some obvious sign...

He's too pigheaded to let it show until it kills him, she realized. Drawing in her breath, she began pushing at his clothes, moving the material from his arms and torso, then his ankles and calves. He was weak almost to the point of immobility, and couldn't have fought her even if he realized what she was doing. Katara was just grateful he'd been stripped of his armor by the pirates; she wasn't sure she would have been able to get it off him.

Eventually she found it: the lasceration was as short as Katara's finger, just a thin slice on his leg. It should have been nothing—shallow, very little blood, quick to scab over. Instead it was a wrinkled, pussy mess, a thin mouth of infection on otherwise unmarred flesh. Through the skin Katara could see red tendrils snaking outward, spreading over nearly his entire leg.

"Oh my god," she whispered. Hastily she scrambled around for the water flask, screwing off the cap. Focusing all her attention on her bending, she drew out the last of the fresh water and elevated it above Zuko's wound. There was a glow, slow and steady, as the purple and red distorion lightened to soft pink skin, and the puss infected opening smoothed over, absorbing the water with it. Breathing heavily from the effort and concentration, Katara moved up to his side, lightly slapping his face to get him to wake up and look at her.

He reacted, but too slowly. His eyes were glazed and unable to focus. He started to speak.

"Where's the anchor? He took it from--"

"Zuko! Look at me!"

He wasn't listening, just mumbling. About the Avatar, about his greedy sister (he had a sister?), about his uncle. He wouldn't shut up and it was starting to make her panic.

"Focus, Zuko, focus! You were cut, and it got infected. I healed it but the infection might have gone into your blood. I don't know what to do!"

"We need to dock in Pisoh, there's a woman who's hunting—"

He must be delirious. She'd never seen a delirious person before. But if heatstroke was affecting him on top of blood poisoning... "Zuko, focus on my voice. You're in danger. In less than a few days you will die. Unless we get medicine immediately. I can last another week but you will die much sooner, Zuko."

Why was she telling him this? It's not like she could do anything about it. It's not like his being lucid would get them to land any faster.

"I tried to tell him you can't send a whole garrison to die. Not for ashes. I tried—"

"You are the one in danger, Zuko," Katara nearly shouted. It didn't matter if she couldn't do anything; she at least had to have him sane. If he was going to die he was going to die awake and aware. With a sound mind and an annoying temper just like always.

"You have to listen to me. There is no garrison. There are no ashes. There's nothing like that here! You're in the middle of the ocean with me, Katara, and you've got a fever. You're hallucinating!"

The shout seemed to reach him, because for a moment he met her eyes and she could see lucidity in them. "Maybe I'm supposed to die out here. Maybe in the end he sent me to die."

"Who are you talking about?" But her throat felt dry, because maybe she already knew. Maybe they'd all known for a long time but never discussed it. Who could order a prince of the Fire Nation to go on a journey with no promise of return? She couldn't help answering her own question, awed horror tinging her voice.

"The Fire Lord."

No. Families don't do that. Families don't do that to you.

Zuko grabbed her shoulder, pulling her face close to his. His breath was old and tasted like salt and charcoal. "Uncle you have to control Zula. She's mad. When we were children, the dogs—with the—you remember the dogs, don't you? She's mad. It's worse than I told you I'm sorry I lied but you can't let her have it Uncle."

"I'm not—"

"Uncle please! You have to control, you have to—to—Zula—"

Katara gave in; if he wasn't seeing her now then there was nothing she could do.

"Okay, Zuko," she said, slowly peeling his gripping fingers from her arm, patting his shoulder with her other hand. "I'll take care of it. Everything will be okay. Your, uh, your unlce's got everything taken care of."

Zuko passed out at her words, and she felt dirty for them.