so we know that the salt will dissolve in the water, but the sand will not dissolve. So it's easier to get rid of the sand first. Get some filter paper, put a beaker or anything else to collect water in, and pour the mixture over the filter paper into the beaker. The filter paper will catch the sand if done correctly.
Now for the salt and water. There are many ways to extract the salt. The first way is electrolysis - creating chlorine gas on one electrode and sodium metal on the other. Then just collect the water. If it's the salt you want, you can evaporate the water off and leave the salt behind.
If it's both salt and water you want, then a distillation may be the way to go. It involved boiling the water, and then collecting it as it condenses again down a tube, leaving the salt (with a very high boiling point)