Sorry no holdfast attached.
Lacy, fine, nearly translucent light brown algae (or possibly seaweed) growing profusely on dock. Clumps 6-12" but hard to tell where one ends and he next one starts because it was so fragile.
ID as per http://www.beachwatchers.wsu.edu/ezidweb/seaweeds/Pterygophera.htm (Note - they have a typo in the genus name and thus URL!)
The Phaeophyceae or brown algae (singular: alga), is a large group of mostly marine multicellular algae, including many seaweeds of colder Northern Hemisphere waters. They play an important role in marine environments, both as food and for the habitats they form. For instance Macrocystis, a kelp of the order Laminariales, may reach 60 m in length, and forms prominent underwater forests. Another example is Sargassum, which creates unique habitats in the tropical waters of the Sargasso Sea....