Take a close look at the long strands of this seaweed, then there is no doubt where it got its name from: long, thin, inflated tubes. Its appearance can vary depending upon where it grows. There are lots of species of gutweed, often growing at the foot of a sea dike, on tidal flats and beaches. Some even grow in fresh water. You can find around ten different species in the Netherlands, which are only possible to identify with the help of a microscope.