There are ways to make that water potable, though, and science is finding even more ways. In order to turn salt water into drinking water, you need to desalinate it first.
This video shows how to distill water using simple and easy to find items. If you were to actually purchase all the items needed this project would only cost $2-5.
That just means that you need to remove the salt. There are many methods for doing this but the most efficient and realistic way to do it at home in a survival situation is by using the distillation by evaporation method.via(survivopedia)
The glass bottle method of distillation is similar to the glass bowl method, but it has a few more advantages. For one thing, when the process is over you will already have the distilled water in a bottle and won’t have to worry about transferring it from a large bowl to a bottle.