The dissemination of the fruits, seeds, and other primordia (the earliest stage of development) of plants downstream by means of the flowing water currents: Hydrochory is typical primarily for marsh and water plants, algae, and some kinds of fungi. The adaptations for this means of transmission are various bulges and growths on fruit membranes or seed coats (or special cells, as in the spores of fungi), which are filled with air and act as floating sacs.

Plants in which hydrochories occur include water plantains, arrowheads, flowering rushes, bur reeds, and pondweeds.