The lakes or streams of Morrowind are often the same: harmless. Except for the creatures living there, nothing threatens us in these waters.

But on Earth, volcanic activity allows for some very strange things: acidic lakes, like the one in the crater of the Kawah Ijen volcano, or basic/alkaline lakes, like Lake Natron.

The first one gives off toxic fumes and it is of course deadly to dive in it.

The second one is more particular: its composition makes that the animals which dive there are transformed into "statues" (they are calcified), and the rare living species in the lake are bacteria which produce a red pigment, giving this blood color to the lake.

Why wouldn't there be such lakes in Morrowind? If there are salt plains in Deshaan, I can imagine a lake similar to Lake Natron, with stone bodies in some places (reminiscent of the salt-covered skeletons of Deshaan). A red color would stand out a lot in this white area, and would give it a "blood lake" aspect, evoking the great danger it represents.

There could also be a very "classic" acid lake. Although I would rather see this kind of lake in Sundered Scar.