"Is there still water in their lungs? Why doesn't it get coughed out once they are out of the water?"
No, it is not as simple as "leftover water from the drowning". Rather, due to the presence of the water in the lungs, which has been presumably expelled entirely, the interior of the lungs becomes irritated and inflamed.
This inflammation process produces it's own fluid which will slowly fill the lungs and "drown" you - especially while you are prone, while sleeping, wherein the fluid pools along the entire length of the lung, rather than just filling up the bottom of the lung.
No, it is not as simple as "leftover water from the drowning". Rather, due to the presence of the water in the lungs, which has been presumably expelled entirely, the interior of the lungs becomes irritated and inflamed.
This inflammation process produces it's own fluid which will slowly fill the lungs and "drown" you - especially while you are prone, while sleeping, wherein the fluid pools along the entire length of the lung, rather than just filling up the bottom of the lung.
It's a misleading term ...