I don’t think so. For one, blood bending involves bending something you can’t see—which Katara has expressed is harder than something you can. A see through bottle is probably a lot easier in that regard. On top of that, blood bending requires more precise movement. You’re bending thin veins of blood, rather than a single bulky mass of liquid in a bottle. I’d imagine that’d make it easier, as well, especially if you’re not too particular about the path it takes to reach you.

It can't bend in the bottle though at it has very little room to flow. Water bending never moves as a single bulky mass, it always ebbs and flows in streams. Otherwise you could just levitate anything with water in it.

What about the blob Katara caught that fish in? That was relatively still water it seemed like. It probably wouldn’t work with unopened bottles, but once you let that initial pressure out there’d be a bit to move it around.

Water bubbles (or balls) emulate water in zero G. It's a natural form (resting state), similar to a raindrop with no wind resistance. It's why waterbending is based off tai-chi. It's all about following natural flows rather than strong, often forceful movements such as in hung-gar (the basis for earthbending). Water bending isn't about controlling water, it's about directing it. That's why Iroh based his technique for deflecting lightning off it. It's also why most waterbenders can't bend when bound. They need their arms to help direct the flow of the water. Those who can waterbend without the use of their arms need to learn how to use their bodies and legs to direct the flow. Bind the water (such as in a bottle) and you'd likely run into similar problems. Notice they can shoot off water and condense it into an ice spear but not manipulate ice itself. They need to turn it back into water.

However, Katara didn't really have a problem bending the water in and out of her little bladder thing, which is pretty much just a bottle, and she didn't have trouble bending the spirit water out of that tiny little flask. I agree with you on the whole directing idea, but i don't think binding the water is an issue in the bottle case because water benders can make the water flow upward and defy gravity. We've seen waterbenders bend water upwards in defiance of gravity in the forms of waves and streams and stuff like that, so i think bending water out of a plastic bottle is just a matter of directing the water up and out first, then into whatever shape you want. I think binding is only an issue when there is absolutely 0 room for the water flow and there is no open space in which to redirect the water. Likewise, it'd either take a very powerful bender or it's impossible to bend water against the natural current, but it's easier to make a whirlpool because a whirlpool is more in line with the current. Bloodbending's always been a curious issue for a multitude of reasons. Katara seems to be able to bend mud, perfume, and soup pretty easily and Hugh from the Foggy Swamp can bend the vines pretty easily as well, but Bloodbending seems to be particularly difficult, even for seasoned masters. While the soup, vines, perfume, and mud all retain the flow-y style of waterbending, bloodbending stands out because it moves in a herky-jerk, stiff, puppet-like fashion. With a quick google search, i think that waterbending only works with ease within about 95% water content and above, but i think there's more to bloodbending than just water content. To me, the reason why bloodbending is such an elite technique goes back to the flow rules: how waterbending gets harder and harder the more a bender resists its flow because our conscience and subconscience are directing the flow of our blood. To bloodbend, a bloodbender must wrest control of the blood's flow from the victim's brain before they can bend, and even then must maintain that control. I'm also curious as to whether the viscosity of water based liquids affects waterbending at all; is molasses harder to bend than juice because molasses can't flow as well?

In an open bottle, sure, but a full, sealed soda bottle has very little room for the water to move around. If they could simply just levitate water, they could just throw people force style, blood bending or no. The vine bending thing is weird but apparently they can't do it with just any plant (implying that those vines have a higher concentration of water) and something about plant cells being different from animal cells. If I had to guess I'd say something about the healing properties of water are in play as well, which is why the vines can seem to stretch and grow. Blood bending is all over the place. It's originally established in [i]TLA[/i] that you need a full moon to do it. Later, in [i]TLoK[/i], it can be done both at any time AND "psychically". Beyond that, literally two people in the world knew of bloodbending in [i]TLA[/i]. By the time of [i]TLoK[/i], it's widely known. So who was out there spreading the technique, Katara or Hama (who was already old AND locked up for life to specifically prevent her from using and teaching bloodbending). [i]TLoK[/i] has the [i]Dragonball[/i] problem where they just introduce ridiculously OP villians to present new challenges. Unfortunately, that meant they had to use the ultimate power: lore bending.

Bloodbending doesn’t necessarily have to be taught by Hama or Katara. The Southern Raiders, and the people in Hama’s village all experienced it first hand, and if they talked about it at all (the Raiders in particular probably would’ve reported that to whoever’s commanding them), then knowledge of Bloodbending would’ve spread, and someone else could’ve independently reinvented & taught it, based on those stories. It’s worth noting I haven’t actually watched Korra, though. If you look at things from a more spiritual side, being able to bend the vines but not another person makes more sense, especially for someone so in tune with nature. I think it [i]only[/i] makes sense if you look at it spiritually, in fact, because it wasn’t just the vines; he used seaweed during the day of black sun, and seaweed’s pretty thin.

Hm.. Okay, fine, you win. There’s still a lot more applications to water bending that wouldn’t damage your surroundings. Stirring soup, making ice, and the obvious answer of healing. And you could still grab your soda from across the room by pulling it out of the bottle! :D

True, healing would be EXTREMELY useful. To be fair though, earth bending construction workers would be a huge boon to city planning. I mean, no city rivaled Ba Sing Se.