Spiral wrack is a small version of bladder wrack, but it doesn't have inflated bladders. The bladders that you may see have a jelly-like content and are for reproduction. The bladders have a narrow rim which is lacking by bladder wrack. This brown seaweed grows in the highest part of the tidal zone, often underneath Blidingia minima. Spiral wrack is fairly common in the delta region and the Wadden Sea.