Partial drowning is when someone survives form a drowning event and appears to be fine. However the water inhalation from the event can cause serious problems, and can be potentially fatal. This inhalation of water can then act as an irritant in the lungs. This causes collapsing of the lungs alveoli, therefore reducing the ability to exchange air. Depending upon the salt content on the water, different types of osmosis can take place. When Freshwater (low salt content) is taken into the lungs it will be pulled into the pulmonary circulation by osmosis. This causes a dilution of the blood known as hemolysis (bursting of red blood cells). Seawater (high salt content) is hypertonic to blood, which causes an opposite occurrence. Osmosis will instead pull water from the bloodstream into the lungs, thickening the blood. When the blood becomes thicker the heart has to do more work to distribute it around the body causing cardiac arrest very quickly. Hemolysis with freshwater can also cause cardiac arrest and this usually occurs quicker than when the blood thickens.