How to make custom river shapes?

i try to make rivers but i have to use water planes, and i’ve seen complicated lava rivers in Jackson Lawrence’s videos, i want to do the same thing but with water.

To create complex river, or any water shape, you will need to use static meshes. You can make these in a free program called Blender.

Thanks, but i JUST figured out how to use the splines, but using Blender i could make my lake with just 1 mesh.