Eelgrass is a seed plant and not a seaweed. It has roots and seeds just like land plants. Mattresses and cushions filled with eelgrass, dikes made from eelgrass for defending the land from the sea - just some of the ways this plant was used before it practically disappeared in the Wadden Sea, Zuiderzee and Delta region. Lots of eelgrass grew in the waters surrounding Wieringen, giving the island its name. The 'wier' was eelgrass. In earlier times, it was harvested and formed a major source of income for residents of the islands. It was a disaster for them when the large eelgrass habitats disappeared, after the closure of the Afsluitdijk.