It had started out all right. Unohana was on the ship somewhere, but she was different (and if he hadn't yet gotten used to those things happening, he was at least capable by now of noticing them when they did), and of all people, Ise Nanao had known (remembered?) his name and spoken politely to him. He had eventually found a way up to the decks, but a very courteous gentleman had shaken his head, turned him away, and given directions to the third-class dining room. So that was that. It wasn't so bad, anyway.
But then that had happened, and the captain announced the evacuation... He had begun to make his way back to the stairs, then, feeling dizzy and sick from the stale air and the blood pounding in his ears. He was neither a woman nor a child, obviously, and even if it had occurred to him then that he might just be able to pass for one or the other, of course he wouldn't have tried it. Still, one couldn't just stay below decks and wait to die, and maybe there'd be something he could do to help. But long before he got close to the way up, he ran into them: the other passengers of this lowest level. Their bodies were cramped too tightly into too small a space for the motion-- which had taken on a life of its own, continuing long after every individual in the crowd had stopped trying to shove into one another (and even after they started trying not to)-- to be properly described as 'teeming'. Whether they were being actively prevented from ascending to the decks or simply couldn't move forward in such close quarters, he couldn't tell, but either way there was no question of going up that way. Besides, the mass of undyed cloth and panic-stricken faces was nothing he understood how to deal with, and he was still far enough away that he hadn't been drawn in among them, so he turned around (unsteadily; the blurred top half of his field of vision still refused to clear no matter how long he stood in one place or shook his head back and forth) and went back the way he had come with one hand on the wall for support.
Someone ran past him, and he stumbled. "Excuse me, please," he called, "but do you know whether there's any other way up?"
"Nah," the person (a man; youngish, although of course Hanatarou was a horrible judge of age) answered, his demeanor suggesting that being spoken to had surprised him. "All blocked off back that way, and no better up this side as I see it. It's nothin' for it." (But nonetheless he resumed running almost immediately, pushed his way into the immobile crowd, and was lost from view. There was no way of telling whether he had heard Hanatarou when he bowed slightly and said "Thank you.")
For a while, Hanatarou walked around looking for a room with a porthole, but was unsuccessful (maybe they didn't have any on this level). He settled for a bare room with various things strewn across the floor and sat down in the opposite corner from an immense pile of dirty sheets.
His senses weren't working right (there was no reiatsu anywhere) and his thoughts kept going wrong. His body was wholly material (it had been ever since he'd first come to the city), so he couldn't just abandon the gigai to its fate and escape as a spirit. Of course, he didn't have any hell butterflies with him. (Nor did he have his zanpakutou, or, apparently, any other powers.)
So this was a 'curse'.
The room spun when he tried to get back up, so he stayed where he was; for lack of anything else to do, he listened to the network for a while. Everyone was frightened... People were in trouble. There weren't enough lifeboats or rescue vessels after all. The people back in the city couldn't seem to reach those on the ship. His heart twisted when he heard voices he recognised, but he didn't answer. They were unreachable. If there was anything he could have said to them, he couldn't figure out what it might be, and he was too afraid he would give away his own situation.
There was no word from Unohana...
He didn't know where she was. Maybe she had made it on to one of the lifeboats.
Asking after her on the network was out of the question, of course. He didn't know how to set up the 'filter' from here, and because everyone was kind, they would worry about him when they heard him say something and figured out what was going on. When so much else was already happening, and when there was nothing anyone could do anyway, it would have been stupid and meaningless.
In any case, Unohana. Assuming she hadn't gotten safely away, then in the first place, he would never find her on this gigantic ship, and in the second, it wasn't as though he would be able to do anything for her even if he did.
And then again, there were probably many other people still trapped, and their lives were worth preserving, too. Moreover, if he gave up now and decided he couldn't do anything, it would make him the most worthless person imaginable. And finally, even if there truly was nothing else, keeping someone from being alone at the very end was 'something'...
So he got up, which was when he noticed that gravity was pulling him down in the wrong direction. (Or rather, that the ship was tilting.) Still, if he clung to the walls as before, he could make a little progress. His search wasn't thorough-- there were too many places he couldn't reach-- but it was systematic. He hadn't been at it for very long when there was a distant groan (not human) and a tremendous shudder, and gravity changed again. And soon he was wading through a shallow, diagonal layer of water that was growing deeper with a quiet, insistent rushing noise. All he could do was keep making his way upward and try to stay ahead of it.
The corridor he was following turned to one side and dead-ended. So it hadn't been any good after all... That was too bad. There was nothing to do anymore but wait. He didn't listen to the network; he was sure that if he did, he wouldn't be able to resist the temptation to call out to someone. For no apparent reason, it suddenly occurred to him that just because the water was only now filling the inside of this part of the ship, that didn't mean it was just now sinking. The entire vessel could have sunk long ago; it was just that the sea was only now penetrating to the remotest corners.
He had never been a strong swimmer, but he knew enough to take off his shoes and the sodden outer clothing that was already weighing him down. He let them fall into the blank darkness with an insignificant splash, and little by little, the water rose up to meet him.
His first thought was that it wasn't as cold as he'd expected, but after only a few seconds he realised he was mistaken. It did seem that the temperature stayed just above the critical level at which he'd simply go numb and be unable to feel it anymore, but at least that meant he wasn't dying yet. Soon he became aware that the horror of desperately trying to hold his nose and mouth above the surface as the space slowly disappeared was not something he was strong enough for, so he filled his lungs and dove down, swimming aimlessly with stiff, clumsy motions. It made no difference to what he could see whether his eyes were open or not. When his instincts told him to rush for the surface, he ignored them. (Which way was 'up,' now, anyway?) The breathing reflex was harder to suppress, and his esophagus began to spasm as the level of oxygen in his blood decreased. The first gulping rush of seawater into his lungs was much more painful than he had anticipated. The next one was worse, but after that the burning edge to the pain subsided greatly. The seconds passed with aching slowness. His body grew heavy, and then began to feel warm. (This was due to the bodily systems that governed his extremities and allowed him to sense temperatures shutting down, of course, but he didn't mind.)
The last moment must have been going on for hours. When he tried to think of how sunshine had felt, the memory wasn't there; he tried again, but by then even the idea of sunshine wasn't there anymore. He tried again, but by then even the word had gone.
He began to feel something again; it filled his entire body, even the parts he couldn't feel anymore, and he was at once deeply grateful and unbearably lonely. It hurt terribly, but the pain was wonderful. Still, in time, that too faded away. Soon there was nothing left.
It felt like going home.