Position so that lungs are higher than mouth, then squeeze chest to expel water. Always try to make gravity your friend.
Hang yourself upside,thats not a joke either ,or have a drain put in to the bottom of the lung ,a tube that is punctured in to the lung through the ribs. Water on the lungs from near drowning in water is drained . If water on the lungs is caused by disease its pointless in draining them as they fill back up although you might have to stay in hospital with a drain if it was life threatening.
Eat
My friend has water on her lungs how can she get rid of it
So if I had to say in hospital how long will I be in to get rid of the water from my lungs