Abstract: An orally operable water filter includes an outer covering formed of a flexible, water impervious material and which defines an elongate enclosure. A flexible microporous filter membrane, having a pore size of not more than one micron, is disposed within the elongate enclosure and divides the enclosure into respective fluid inlet and fluid outlet compartments, such that the outlet may be placed in the mouth of the user and the fluid inlet may be contacted with a source of water to be filtered by drawing the water through the filter using oral suction. Furthermore, the filter includes a flexible separator, disposed at least in the outlet compartment, for preventing the blocking of fluid over the surface of the filter membrane.