I need you guys to help me out here. I'm developing clothing ideas and I need to understand what animals and plants may be used to create such clothes.
Part of a story that I'm creating is a water country and most of the land is moist, wetlands, ponds, willow trees, victoria amazonica, crocodiles, turtles, beavers, possums and so on.
I need some names of species of AMPHIBIAN creatures or plants that can be used for making clothes from this kind of environment.
To make clothes you need fibers.
Posidonia oceanica is well known for the fibrous balls it leaves on the mediterranean shores.
If those fibers can resist decomposition from sea water, they are good candidate for making durable water clothes.
Another well known source of fibers are fishing nets and fishing lines used by homo sapiens sapiens, made of durable nylon which can be used to weave clothes.
You can make leather from amphibian hides. Here is a hat made from cane toad leather.
I was disappointed that my search did not turn up anyone wearing tight pants made of cane toad leather. If someone there can find such an image please edit this answer to add it!
Cane toads are little. But amphibians can get big. Giant salamanders still exist. That one is a sweet shade of pink, which would make some excellent tight pants.
Salamanders this big live like crocodiles: ambush predators. They have awesome faces. One was found recently thought to be over 200 years old.
My answer: make your stuff out of salamander skin.
There have been other questions that have touched on the leather thing, like this one. Pretty much, the biggest problem for an aquatic nation is that you actually need land and drying time in order to make leather. You don't have the hurtle, you are just using the land/water as a resource.
Amphibian is a weird word, because it can have different definitions depending on who you ask. Scientifically, we're talking frogs, newts, salamanders, that kind of thing. Historically, according to the Greeks, things that lived in and out of the water, like, say otters and your crocodiles.
While the Chinese giant salamander is large enough to make leather from on a larger scale, I can't find any evidence that anyone ever actually has. There's a Salamander Bonded Leather Company, but that seems to only be the name, and so salamanders aren't actually involved. However, don't let that stop you from doing so in your fictional world. The environment they live in sounds more like mountain streams than it does swampland, so it may not fit what you are doing.
However, when it comes to toads and frogs, there actually are places selling that.
The main problem is size, because you'd have to piece together small frog "pelts" to even make an outfit.
The answer to that is either giant frogs, which I fully endorse, or a type of bonded leather, where leather is:
made by shredding leather scraps and leather fiber, then mixing it with bonding materials. The mixture is next extruded onto a fiber cloth, or paper backing, and the surface is usually embossed with a leather-like texture or grain. Color and patterning, if any, are a surface treatment that does not penetrate like a dyeing process would. The natural leather fiber content of bonded leather varies. The manufacturing process is somewhat similar to the production of paper. SOURCE
Or you can just have them sew it all together.
AS far as thread and fabric is concerned, since you are building a world, and although this isn't what you asked for (since it is more sea life, though it could show up in a swamp estuary), there's byssal threads from mussels.
Now, looking at plants, the thing is that tech level is very important as far as answering this. Today's list of plants that can be made into fabrics is extensive, and many were unthinkable just 20 years ago. Reeds, straw, and bamboo can be made into fabrics. Really, most are just converted into rayon.
Give me a tech level, and I can start to answer as far as plants are concerned. With the right manufacturing, lots of stuff can be used that way. But if it's low tech, then you have a problem.
There's good news though. If you aren't married to it being a plant that grows IN the water, flax may be surprisingly your best bet.
Flax is often found growing just above the waterline in cranberry bogs. Heavy clays are unsuitable, as are soils of a gravelly or dry sandy nature. Farming flax requires few fertilizers or pesticides. Within eight weeks of sowing, the plant can reach 10–15 cm (3.9–5.9 in) in height and grows several centimeters per day under its optimal growth conditions, reaching 70–80 cm (28–31 in) within 50 days.
