This aptly named bright grass green seaweed forms an inflated, tube-like frond which resembles an intestine. Length up to 80cm.
Found attached to rocks and stones on sandy or muddy shores, in sheltered estuaries and rock pools on the upper shore. A common and widespread species.
Photographs taken April 2013, Llandudno, Wales, and August 2015, Meadfoot Beach, Torquay, Devon.