The green laver is thin bladelike green algae often seen in the low intertidal zone and in shallow waters. It is so thin that it is almost opaque, it only one cell in thickness. It is also called sea cellophane.
The green laver is perfectly edible, dry it first, then roast and crunch. Closely related species are cultivated in the eastern Asia and is a popular part of some sushi dishes.
Two other Green algae species are very similar and we are never 100% certain which is which on photos. These are the sea lettuce (Ulva lactuca) and the dark sea lettuce (Ulvaria obscura). These two are usually more robust than the green laver.