- Kingdom: Plantae
- Phylum: Chlorophyta
- Class: Ulvophyceae
- Order: Ulvales
- Family: Ulvaceae
- Scientific name: Ulva lactuca
- Norwegian: havsalat
As the name indicates, this edible green seaweed, looks like lettuce. The flat, green fronds have ruffled and often torn margin. It is usually 10-20 cm of height and may have a diameter of 30 cm. This is the most common green algae in Norway, but there are other Ulva species which may easily be confused the common sea lettuce.
If is usually found on a hard surface between the subtidal zone and a depth of 15 meters. It may also grow on larger algae.
It is widespread in all oceans.