Choking on water should be treated accordingly to the amount of water choked. Generally, if the amount of water choked is small, the liquid can be coughed up through the cough reflex of the lungs. If swimming a lot of choking need to promptly remove the oral cavity dirt, prone position drainage, if necessary, need to do cardiopulmonary resuscitation.
When drinking water, the gas in the mouth is not exchanged effectively with the outside world, and the water enters the lung trachea as a result. Generally choking a small amount of water, usually there will be a lung reflex cough, more than can be discharged through coughing the water.
If there is a large amount of choking when swimming, you should first remove the dirt in the mouth and nose, so that the airway is open, use the prone position to drain the water, if necessary, CPR can be carried out after the arrival of first aiders to give standardized treatment.
If you do not have experience in dealing with this, it is recommended that you seek medical attention in a timely manner, with the help of a doctor.