Adult hippos can hold their breath underwater for about five minutes, sometimes up to six or seven minutes, although they usually resurface every three to five minutes to breathe

. They close their nostrils and ears to prevent water from entering while submerged and can even sleep underwater using a reflex that allows them to surface for air without waking

. Newborn hippos, however, can only hold their breath for about 30 to 90 seconds, with most sources citing around 40 seconds to 90 seconds for infants

. Mothers often push newborns to the surface to breathe if they are born underwater

. In summary:

• Adult hippos: hold breath for about 5 minutes (up to 6-7 minutes)
• Newborn hippos: hold breath for about 30-90 seconds

This ability supports their semi-aquatic lifestyle, allowing them to spend up to 16-18 hours a day in water to protect their sensitive skin and regulate body temperature