Description: Sporophyte forms small tufts of filaments up to 3 cms long, irregularly branched. Sporangia lateral. The Gametangial phase is spherical growing on, and penetrating, encrusting coralline algae.

Habitat: Uncommon. Sublittoral to 20 m.

Distribution: Widespread around the British Isles. Europe: Mediterranean, Norway and the Faroes. Greenlands. Atlantic coast of North America: Canada, Massachusetts, North Carolina. Further afield: Canary Islands, Jamaica, Mexico, Bahamas, Brazil, the Pacific from Alaska to Baja California, Japan, South Africa and South Australia.

Similar Species: Derbesia tenuissima. The difference is microscopic.

Distribution Map from NBN: Derbesia marina at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Derbesia marina at iNaturalist World Species Observations database.

WoRMS: Derbesia marina at World Register of Marine Species.