Fun quick stop. You can do this was in 15-30 minutes. Beautiful and easy walk.
If you don't go at low tide, you won't be able to walk out to it. The navigation from road trippers led us down a forest service road to a dead end- so make sure you follow the main road to Rialto beach. You walk north along the beach to the rocks. Also on the Rialto beach is the redwood tree to check out.
We made a quick stop at the tree root cave. Just a few hundred feet north of the parking lot at the camp grounds. Go at low tide so you can explore the beach as well.