An osmotically driven fluid dispenser for use in an aqueous environment comprising: a shape retaining canister having controlled permeability to water; an osmotically effective solute confined in the canister which, in solution, exhibits an osmotic pressure gradient against the water in the environment; an outlet in the canister wall; and a flexible bag of relatively impervious material that holds the fluid to be dispensed and is housed in the canister with its open end in sealed contact with the canister such that the canister outlet communicates with the bag interior and the bag interior is closed to the solute and aqueous solution thereof with the remainder of the bag spaced from and generally unsupported by the canister wall.