Channelled wrack is a small sturdy brown seaweed with gutter-shaped grooved stems. It has a smooth surface with no midrib. Channelled wrack is found high up in the tidal zone on dikes, even higher up than spiral wrack. That means it is often exposed to the air. To prevent drying up, it is covered in a layer of mucus. In addition, the gutters (channels) in the stems can retain water. Channelled wrack is only found in the Oosterschelde in the Netherlands. Due to a decreased tide resulting from the storm-flood barrier, even there it is growing rare.