The “water fairy” or “water immortal” (水仙花) is the multi-headed flower Narcissus tazetta var. chinensis, with white petals and short yellow trumpet – A “golden goblet on a silver tray.”   The waving leaves are “the immortal on the waves.”   Narcissus is a flower of winter, announcing spring, and it is often used in images for the Chinese New Year, good fortune, prosperity and longevity.    Narcissus with plum blossom signifies the change from winter to spring.

I love the meticulous handscrolls by Zhao Mengjian (Song dynasty), like this one in the Met.  Copying just a small section of the one from the Tianjin Museum shows how to compose the flowers.

Then you can easily do a free-brush version.