Quillworts are mostly aquatic or semi-aquatic in clear ponds and slow-moving streams, though several (e.g. I. butleri, I. histrix and I. nuttallii) grow on wet ground that dries out in the summer.
Isoetes eludens is an aquatic plant in the genus commonly known as quillwort that is native to the Kamiesberg Mountains in Namaqualand, South Africa.