Mugger crocodiles have 19 upper teeth on each side; a snout that is 1⅓ to 1½ as long as broad at the base; a rough head but without any ridges; mandibular symphysis extending to the level of the fourth or fifth tooth; pre-maxillo-maxillary suture, on the palate, transverse, nearly straight, or curved forwards; and nasal bones separating the pnemaxillaries above. Four large nuchals forming a square, with a smaller one on each side; two pairs of smaller nuchals on a transverse series behind the occiput. Dorsal shield well separated from the nuchal, the scutes usually in 4, rarely in 6, longitudinal series, those of the two median usually considerably broader than long; 16 or 17 transverse series. Scales on limbs keeled. Fingers webbed at the base; outer toes extensively webbed. A serrated fringe on the outer edge of the leg. Adult blackish olive above: young pale olive, dotted and spotted with black. The largest specimen in the British Museum measures 12 feet, but individuals are said to grow much larger. On average, females are 7.4 feet (2.45 m) and males are 10 feet (3 m). Old, mature males can get much larger, at up 4 to 5 m (13-16.5 feet) and the largest animal recorded was 16.8 ft. Individuals exceeding 14 feet are exceptionally rare, and these can weigh more than 450 kg (1000 lbs). Mugger crocodiles can achieve speed of around 8 mph over a short distance in pursuit of prey.They can swim much faster 10 to 12 mph in short bursts,when cruising they go at about 1 to 2 mph.
Mainly a freshwater species, the mugger crocodile is found in lakes, rivers and marshes. Muggers prefer slow-moving, shallower bodies of water rather than, fast-flowing, deep areas. Also known to thrive in man-made reservoirs and irrigation canals. Although it prefers freshwater, it has some tolerance to saltwater therefore is occasionally reported from saltwater lagoons. It is sympatric with the gharial (Gavialis gangeticus) in some areas of India and with the saltwater crocodile (Crocodylus porosus) in other areas, but separated by habitat most of the time. It is adapted to terrestrial life like its cousin, the Cuban crocodile, more than most crocodilians, but is ecologically most similar to the African Nile crocodile. It is known to be more mobile on land, can migrate considerable distances over land in search of a more suitable habitat. It can chase prey on land for short distances. They are also known to dig burrows as shelters during the dry seasons.