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A small family comprising six species of very distinctive water beetles included in the genus Hygrobia Latreille, 1804. One species, H. davidi Bedel, 1838, may be extinct; it is known from a male specimen collected in Jiangxi Provence, Southeast China, which is now stored in the Museum d’Histoire naturelle in Paris. Four endemics occur in Australia; H. nigra (Clark, 1862), H. wattsi Hendrich (2001), H. maculata Britton, 1981 and H. australasiae (Clark, 1862) and all are rare. The final species, H. hermanni (Fabricius, 1775), is very local but widespread throughout Europe and North Africa. They are commonly known as screech beetles due to their habit of stridulating loudly when alarmed; the sound is produced when the sharp edge of the seventh tergite is rubbed against a median subapical file on the elytral undersurface. Adults and larvae of all species inhabit stagnant water where the substrate is layered with fine mud and decayed plant debris. Both stages are predatory. The adults are characterized by the following features: Size up to 10mm. Body very convex above and below. Glabrous or nearly so and densely punctured.  Tarsi always 5-5-5. Eyes protuberant and remote from the front margin of the pronotum.  The presence of an antecoxal sclerite; a small transverse sclerotized plate lying between the posterior edge of the metasternum and the post coxal processes. The adults are strong swimmers, using alternate strokes of the hind legs as they move. The larvae are compact with a conspicuously broad forebody and large head onto which the labrum is completely fused. There is a series of setose gills between the prothorax and the third abdominal segment. They are readily separated from other water beetle larvae by the elongate terminal abdominal segment with its three long and hairy appendages.