Take the person out of the water, dry them, and then wrap them in warm blankets. Call 911 in the US for immediate professional health care and transport to a hospital.
In a very very cold place. But it's not the whole answer- it can happen anywhere that has the right conditions to make your body temperature drop severely. So yes, in those places, but it can...
Hypothermia means below-normal body temperature. Hypo means "under" or "below" and therm means temperature. Hypothermia is when your core body temperature drops. You are normally about 98.6° F (37°...