From Antioch to Tomales Bay, park visitors have reported otters rolling in mud, gnawing on crayfish, sliding down rocks and generally partying on the creek banks. A Marin group has even created an Otter Spotter website, where the public can log their otter sightings on an interactive map and learn more about the charismatic carnivores.
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2012/04/14/BAEO1O1KPR.DTL