Don't ask me where...but I have often heard that drowning in salt water is less painful than drowning in fresh water.
At first I thought this was true because the salt in seawater kills brain cells after it has entered the blood stream.
However, I recently learned that this is not true. Salt water has higher concentrations of dissolved substances than blood and body tissues, so it is unlikely to enter the circulation. This means water is more likely to move from the capillaries of the lung into the air spaces containing the salt water (due to osmosis).
In contrast fresh water is more likely to move into the capillaries from the air spaces of the lung because of the higher concentrations of dissolved substances in blood and body tissues.
The best explanation for this "phenomenon" would be that seas and oceans tend to be cooler than fresh water, so you are more likely to develop hypothermia. This will cause drowsiness and confusion with the result that the person may be less aware of the watery end awaiting them. This is where the myth about drowning in salt water being less painful than fresh water may come from - the drowning person is pleasantly numb to the experience.