The Au Sable turns east and gathers the flow of the East Branch at the town of Grayling. A few miles east of Grayling the river flows past Burton's Landing, which is the start of the fly fishing only, catch-and-release section also known as the "Holy Water." This area extends for nearly nine miles downstream to Wakeley Bridge. Within this stretch, the river consists mainly of sand and gravel. Beautiful trout-filled pools, runs, and riffles litter this section. This is a very productive and also popular area due to the special regulations put upon it and the diversity of the water. These eight miles, which have been designated fly fishing only are not called "Holy Water" for nothing.

Several access points are available to wade or float from. Thendara Road and Stephan Bridge are a couple of the many areas with good access. The water is fairly large but easy to navigate and wade.

The Au Sable National Scenic River is a 23-mile portion of the Au Sable River that stretches from Mio to Alcona Pond. President Ronald Reagan signed the law establishing the segment of the river as a National Scenic River on October 4, 1984.  By receiving this designation, this free-flowing segment from below Mio Pond to the upper end of Alcona Pond received national recognition for its outstanding and remarkable scenic, recreational, biological, and historical values and a national commitment to its protection.  People have enjoyed the scenic beauty of the Au Sable for hundreds of years.

In pre-European settlement times, Native Americans used the river as a travel route.  After the European settlement of the area, the Au Sable River was a major throughway for floating white pine to sawmills or waiting for barges at ports on Lake Huron. During those years many of the logs and fallen trees that littered the river were carried downstream with the harvested white pine. In recent years efforts have been made to replace logs in the river to help reduce erosion and maintain the world-class trout fishing river as an aquatic habitat.