Hippos are a semi-aquatic mammal, usually inhabiting shallow lakes, rivers, and swamps. The water must be deep enough for the hippo to submerge its entire body in; usually water about 2 meters deep is preferred. During the daytime, herds prefer to sleep in shallow water, or occasionally on a mud bank, grouped closely together. It is in these waters that mating and childbirth occurs. When shallow waters are not present hippos reside in deeper water, leaving only their nostrils above the surface to breathe. Hippos emerge from water at dusk and go ashore to feed, and travel individually down familiar paths usually less than 1.6 km to dense, grassy grazing areas along the banks of the water.Hippos are a semi-aquatic mammal, usually inhabiting shallow lakes, rivers, and swamps. The water must be deep enough for the hippo to submerge its entire body in; usually water about 2 meters deep is preferred. During the daytime, herds prefer to sleep in shallow water, or occasionally on a mud bank, grouped closely together. It is in these waters that mating and childbirth occurs. When shallow waters are not present hippos reside in deeper water, leaving only their nostrils above the surface to breathe. Hippos emerge from water at dusk and go ashore to feed, and travel individually down familiar paths usually less than 1.6 km to dense, grassy grazing areas along the banks of the water.