This is an extra chapter, more explanatory, in response to some comments about Chapter 11 and earlier ones.
It's possible that it wasn't entirely clear how Sokka's waterbending works, or what its limitations and consequences are. And that's natural: Sokka himself wasn't fully aware of how his power worked, or even that something was wrong.
What happened to Sokka in Chapter 11?
What occurred — the extreme weakness, the vomiting of blood, the collapse — was a consequence of how he received his ability to bend water. The Moon Spirit granted him, in a spiritual way, a small amount of its chi. But since it wasn't a full physical transfer (the spirit isn't present in a tangible form), that energy was insufficient and unstable.
Sokka has, so to speak, a limited spiritual battery for using waterbending. Every time he bends water, that battery drains a little. If he uses it moderately, it has time to recharge by gradually and gently drawing from Sokka's natural chi.
But if he pushes it too far — like in Chapter 11, where he used large amounts of water over a long period — the spiritual energy runs out completely. And when that happens, the system goes into "emergency mode": it begins to rapidly and uncontrollably absorb Sokka's life-force chi directly.
That's why he collapsed.
His body was being drained from the inside to sustain a power that didn't fully belong to him.
That's why he had to absorb someone else's life energy (Chi) to recharge the spiritual energy and stop it from consuming his own. It was a terribly logical thought that Sokka came to — because if he didn't do it, he would die.
In short: if Sokka uses waterbending carefully, the energy will gradually replenish, and he'll be fine. But if he drains it completely without allowing it to recharge, he'll pay the price with his life.
I hope this explanation helped clarify what happened. Thank you for reading.
There may be a new chapter today, and if not, there will be one tomorrow without fail.