Fishing cats are the largest of the Prionailurus cats. They are about twice the size of a domestic cat and have a stocky, muscular build with medium to short legs. The coarse fur is olive-grey with dark spots arranged in horizontal streaks running along the length of the body. The face is elongated with a distinctly flat nose and ears set far back on the head. The underside is white, and the back of the ears are black with central white spots. There are a pair of dark stripes around the throat, and a number of black rings on the tail. Their head-to-body length typically ranges from 57–78 cm (22–31 in), with a short tail of 20–30 cm (7.9–11.8 in), which is one half to one third the length of the rest of the animal. They weigh from 5–16 kg (11–35 lb). The face is spotted and the ears are short and rounded. Black spots run longitudinally across the body, and six to eight dark stripes run from behind the eyes to the nape. The underside fur is longer and often overlaid with spots.
Their feet are less completely webbed than of leopard cats, their claws incompletely sheathed. Webbed feet have often been noted as a characteristic of the fishing cat, but the webbing beneath the toes is not much more developed than that of a bobcat.
Fishing cats are strongly associated with wetland, and are typically found in swamps and marshy areas, oxbow lakes, reed beds, tidal creeks and mangrove areas and are more scarce around smaller, fast-moving watercourses. Most records are from lowland areas. Although fishing cats are widely distributed through a variety of habitat types including both evergreen and tropical dry forest, their occurrence tends to be highly localized. They are allegedly found at elevations up to 5,000 ft (1,500 m) in the Indian Himalayas.
As the name implies, fish is their main prey. A one-year study of scats in India's Keoladeo National Park found that fish comprised approximately three-quarters of the diet, with the remainder consisting of birds, insects, and small rodents. Molluscs, reptiles including snakes, amphibians and carrion of domestic cattle supplement their diet.
The solitary living fishing cats are thought to be primarily nocturnal. They are very much at home in the water and can swim long distances, even under water. Females have been reported to range over areas of 4 to 6 km2 (1.5 to 2.3 sq mi), while males range over 16 to 22 km2 (6.2 to 8.5 sq mi). Adults have been observed to make a "chuckling" sound and likely have other calls similar to those of domestic cats.
They hunt along the edges of watercourses, grabbing prey from the water, and sometimes diving in to catch prey further from the banks.
They mark their territory using cheek-rubbing, head rubbing, chin rubbing, neck rubbing and urine-spraying to leave scent marks. They also sharpen their claws and display flehmen.