I believe this is a shaggy mouse nudibranch. It was found in an area that has a thriving population of aggregating anemones (Anthopleura elegantissima) - it's main food source. Spotted at Constellation Park in West Seattle.
Found at low tide in an area with many aggregating anemones.
It was found during the same time of year they are normally laying eggs, but I didn't spot any eggs on this outing.
Lat: 47.57, Long: -122.41
Spotted on Apr 6, 2015
Submitted on Apr 8, 2015