Bubbles of Seaweed

I was walking along the Swan River yesterday afternoon with a friend chatting about all the good things in life when I realised that the seaweed washed ashore was different than normally. They were shaped in little green balls made of rolled weeds. I first thought it was rolled up by the waves but it looks more like a special kind of seaweed which grows like that as there was so much of it in that area in Claremont.