Water Transitions Brackish water is a fairly salty mixture of freshwater and sea water. It is unique in numerous ways and is a life giving ecosystem. To understand what brackish water is, a background should be known about its sources. First of all, there is freshwater. Out of all the water on the planet, only three percent of it is fresh, and only one fiftieth of one percent is readily available. Freshwater is not pure in that it contains minerals and other particles. There are numerous plants and animals that depend on freshwater for their lives. Humans are one of them. Seventy percent of the human body is made up of freshwater (744 Headlam)