Phylum: Chlorophyta Family: Ulvaceae
Ulva intestinalis Linnaeus, 1953
Hollow Green Seaweed; Gut Weed
Widespread and found at all levels of the intertidal zone. In areas of low salinity, such as edges of rock pools and estuaries, where rainwater dilutes the saltiness, it can be a vivid green
References:
Fish & Fish (2011) - A Student's Guide to the Seashore;
Bunker, et al - Seaweeds of Britain and Ireland;
Brodie, et al - Green Seaweeds of Britain and Ireland