San Diego County, California, US
in the water the left half of the picture
I think? Maybe a plant.
Egregia menziesii is a species of kelp known commonly as feather boa kelp. It is native to the coastline of western North America from Alaska to Baja California, where it is a common kelp of the intertidal zone. It is dark brown in color, shiny and bumpy in texture, and may reach over five meters long. It grows a branching stipe from a thick holdfast. It bears long, flat, straplike fronds lined with small blades each...