Phylum: Chlorophyta   Family: Cladophoraceae

Cladophora hutchinsiae (Dillwyn) Kützing, 1845

Dark green when viewed 'en masse', quite long and much branched. Most prominent in the mid-tidal zone and common. Very similar to other Cladophora

References: 
Brodie, Maggs & John (2007) - Green Seaweeds of Britain and Ireland