It's a natural swimming hole created by a series of dams along the San Gabriel River. It's free, and you can take your dog. Lake Granger is an excellent alternative to the Highland Lakes which can have hour-long waits for boat launches in the summer. There are swimming beaches at Wilson H. Fox Park on the southeast end and at Friendship Park on the northeast end. Swimming beaches are grassy, not sandy, and lead right to the water's edge.
Gentle waves lap at the shore, and the lake has a pebbly bottom.
Sheltered, individual picnic areas on the grass look out over the swimming area. Lake Somerville is an impoundment of Yegua Creek, the main tributary of the Brazos River. At Big Creek Marina on the north side of the lake there is a convenience store and camping area. The marina has leased a part of the park on a peninsula and provides excellent swimming and scenic overlooks. The other swimming beach is at Birch Creek Unit, which has a 150-foot long rock jetty.