What is the spring water on the Seine?

A song from the Internet called Mai:

Sister's legs are not legs, the spring water on the Seine.

Sister has no back, Bulgarian rose.

Sister's waist is not waist, but a machete to kill Saburo.

. Sister's mouth is not a mouth, the clear water under Anhe Bridge.

The lyrics of this song describe my sister's legs with the spring water on the banks of the Seine, which means to praise my sister's legs for being beautiful. Later it was widely quoted to praise people with beautiful legs. "