When water enters the nose and mouth the respiratory tracts start cramping. When the cramps subside, the water enters the lungs.
Other injuries from a drowning incident are irregular heartbeat, pneumonia and kidney damage.
Even if the person almost drowning seems ok after a short while, there might be water in the lungs, pulmonary edema. This is called secondary drowning. The person is short of breath and anxious. You should call 112 if this happens after an drowning incident.