I have always wondered myself is salt water would freeze and the answer is yes if it is cold enough. When rain water freezes, you use salt to melt it, right? The temperature would have to be -21 degrees Celsius before salt water will freeze. You can find more information here: http://van.physics.illinois.edu/qa/listi...

It really depends on the amount of salt in the water but the average salt water is the sea which will freeze at 28 degreed Fahrenheit or -2 degrees Celsius.