Agua I was told by a park ranger is the jewel of the San Diego park system. The park is nesseled between two hills which act as a funnel for natural spring water. That spring water is used to feed three pools with one sulfur indoor which is around 106 degrees. It's the perfect place to relax. This is a perfect weekend escape from the city. There is no cell service. To get service you have to go to the cell phone lot 4 miles west at Vallecito campground.