Elatine hydropiper

Elatine hydropiper (vernacular name: eight-stamened waterwort)[1][2] is a species of flowering plant belonging to the family Elatinaceae.

[3] Its native range is Europe to Russian Far East.

[3] It was first described by Swedish botanist Carl Linnaeus in 1753.

[3][4]

https://tropica.com/en/plants/plantdetails/Elatinehydropiper(141TC)/18759
Flowering Elatine hydropiper
Distribution map of Elatine hydropiper in Poland (in regions) (source: A. Zając & M. Zając (red.)