Dry Water

Want a challenge - try explaining dry water to a kid. One hell of an evening it was.

One of the problems with water comes from fact that it is, well, wet. Easy to spill, easy to contaminate, just overall a hassle to transport. Solution? Turn it into a solid object and stack up however you want. Downsides? Well, water does not normally do that.
This is one of cases where Forbidden Forest actually gave us something good. A particular plant (or rather a herb) from there has a natural ability to accumulate water as means of protection against wildfires. Once discovered, the plant became actively sought after by ship crews preparing for long voyages as well as army intendants.

Manufacturing

1. Take intact Dry-Water plants (such an original name), stem and leaves all together.
2. Submerge them fully in cold water. It is better to use a big vessel and many plants at once, so they have ample space to expand. Adding any alcohol instead of water, no matter how weak, will just kill the plant instead.
3. Start very slowly heating it up. This is the most delicate moment of process, as plant is otherwise very vulnerable to heat and can easily get damaged. After a while, you should notice the plant start to expand - this means the plant has noticed the danger and started to soak in water.
4. Once about twice its original size, bring the water to boil and keep it there for up to a day or until completely dry. Congratulations, now you have a very large and hard plant or a bunch of them. Given their weird shapes, plants tend to intertwine a lot.
5. Now you have to immediately cool down the plants, as fast as possible. Most common method is to submerge them in an ice bath. If the plant is allowed to cool down naturally, it will gradually release all its water.

The scholars and alchemists working with Dry-Water plants focus mainly on two things: how to make it soak more water and how to lose less water while cooling down. Drying the plant normally makes it completely useless but experimental methods result in higher absorption per volume, as well as incredibly high costs involved. As for zero-loss cooling, most seargue that is physically impossible.

Utility

The inverse process is fairly simple. You simply heat up the plant and let it slowly cool down, the way it normally would. Over a few hours, the plant will fill out your pot with water and can be put away for reuse. Alternatively, the plant can be crushed to little bits - each tear causes the surrounding areas to release all their water.
It is the latter approach that has caused a number of problems with Dry-Water plants stored on ships. Imagine two ships locked in battle, and a cannonball hits another ship's water storage. What do you think happens next? Right - all the plants quickly turn to water, which can prove...a little problematic, especially if the crew has not prepared for it. On the other hand, some crews have been known to surround their gunpowder kegs with Dry-Water plants as means of protection.

Discovery

Imagine the shock of a traveller who tried to make soup with some of local plants and herbs only for them to suck in all the water instead.