Water rock-bristle has only ever been recorded from two places in Britain. It is thought have been lost from the only Scottish site as a result of a fall of the stream bank on which it grew (2). It still persists in small numbers at a site in south Northumberland (2). This moss is endemic to Europe, but is endangered, and is known from single sites in the following countries: Austria, Germany, France, Norway, Romania, Sweden, and Switzerland. It is also known from three sites in the former Yugoslavia (1) (2).