Salty water won't help you hydrate, but it's very helpful to the human body. Swimming in salt water has been known to help skin conditions and clean and heal wounds. Minerals in salt water can help aching muscles and relieve stress, as well as keep your central nervous system healthy. It's important to note that most of salt's beneficial health properties come when it's diluted in water as opposed to adding it to your food.
When it comes to oral care, salt water can also be beneficial. Rinsing once per day with hot salt water can help to prevent gum disease and plaque buildup. It can also provide immediate relief to sore gums by helping to dehydrate the harmful pathogens in your mouth. This means that salt is helping to kill the bacteria that build up behind your plaque and tartar. For overall gum health or if you have sore gums, try about 1 teaspoon of salt per cup of warm to hot water, making sure it's completely dissolved, and then swish it for 60 seconds.