This largely nocturnal species (5) inhabits burrows during the day and emerges to feed on invertebrates at night (2). They dive under water to obtain prey such as freshwater shrimps and caddis fly larvae, and the occasional frog newt or small fish may be tackled (2). When diving, the water-resistant fur holds bubbles of air that give the shrew a silvery appearance (4). They can also hunt on land for worms, beetles and other terrestrial invertebrates (4). Shrews are well known for their voracious appetites; water shrews must eat about half their own body weight in food every 24-hours to stay alive (6). Unusually amongst mammals, this species has venomous saliva, which aids in stunning prey (2). This species frequently grooms itself carefully, especially after diving. Water is removed by shaking and scratching, and also by squeezing through their narrow burrows (6).
Water shrews are solitary animals, and hold territories (2). They do not hibernate, but are active throughout the year (2). Breeding takes place between April and September (5); during this time 1 or 2, but occasionally 3 litters of 3-15 young are produced in a nest of woven grasses (2) after a gestation period of 14-21 days (4). The lifespan is short (between 14 and 19 months); adults die after breeding, and the young breed the following year (2). Predators include tawny owls, barn owls, foxes, predatory fish and kestrels (2).