Anyone who draws or paints will know that mastering the art of creating realistic water images is very difficult and requires different skills and techniques compared to drawing other objects and textures. Because water is transparent, it takes on.
Sharpie Sketches - Horses by ColossalBeltloop . I once heard an artist say that she liked to draw in pen because there was no erasing, and it helped her learn to accept imperfections. That seems like a good (albeit somewhat painful ) idea!