It includes three living species widespread across Europe, Asia, Africa and Australia.

The genus name of Caldesia is in honour of Ludovico (Luigi) Caldesi (1821 - 1884), an Italian politician and botanist.

Leaves all basal, floating or aerial, ovate to elliptical, cordate or subcordate.

Carpels few or numerous in a single whorl, free, each with 1 ovule; styles subventral.

Fruitlets drupaceous, with woody endocarp and spongy exocarp, swollen, with a short subventral beak, smooth or with tubercles or spines.