Hippopotami are herbivores which live in groups. Despite being semiaquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. They usually stay in the mud and water during the day and come out to eat grass or leaves at night. Though they are bulky animals, hippopotami can gallop at 30 km/h (19 mph) on land but normally trot.