Porphyra umbilicalis

Porphyra umbilicalis, commonly called "laver", is a species of seaweed in the genus Porphyra. It is smooth in texture and forms delicate, sheetlike thalli, reaching 25 centimetres (10 in) long and often clinging to rocks. Porphyra is classified as red algae; it tends to be a brownish colour, but boils down to a dark green pulp when prepared. It is unusual amongst seaweeds because the fronds are only one cell thick.

It is commonly found around the west coast of Great Britain and east coast of Ireland along the Irish Sea, where it is also known as "sleabhac" or "slake". It is edible and used to make laverbread.