Medium to tall plant with aerial leaves narrow to broadly arrow shaped and with pointed basal lobes, long stalked. The submerged leaves are narrower and translucent. Flowers white, 20 to 26 mm, the petals with a basal purple blotch, borne in whorled racemes or panicle.

Grows in still or slow moving water between 10 and 50 cm deep.

July and August.

Perennial.

Widespread in the southern half of Britain, but somewhat local. scarcer elsewhere.

Local but sometimes frequent in suitable areas of Leicestershire and Rutland. In the 1979 Flora survey of Leicestershire it was found in 92 of the 617 tetrads.