Arrowhead

Sagittaria sagittifolia (also called arrowhead due to the shape of its leaves) is a flowering plant in the family Alismataceae, native to wetlands throughout the temperate regions of Europe and Asia; in Britain it is the only native Sagittaria.
It is a herbaceous perennial plant, growing in water from 10-50 cm deep. The leaves above water are arrowhead-shaped, the leaf blade 15-25 cm long and 10-22 cm broad, on a long petiole holding the leaf up to 45 cm above water level. The plant also has narrow linear submerged leaves, up to 80 cm long and 2 cm broad. The flowers are 2-2.5 cm broad, with three small sepals and three white petals, and numerous purple stamens.