Halidrys or 'sea oak', is a very common brown weed that is often seen just below the low water mark, and will sometimes be found growing in rockpools on the lower shore. The highly branched seaweed has small air bladders that keep the plant upright, and it will often be covered in attached red seaweeds and animals such as feather stars which use it as a support.
Halidrys (Photo: Paul Tyler)
The small elongated bladders on this plant make it easy to recognise. They lift the plant towards the light, increasing its ability to photosynthesise.
by Paul Tyler