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. It's understandable that Dutch people think it's a seaweed. 'Wier' in Dutch means seaweed. The northeastern corner of the province North-Holland is called Wieringen. It used to be an island up till the 1920s. Lots of so-called wier grew in the surrounding water, 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, including Wieringen. It was a disaster for them when the eelgrass disappeared in the 1930s. There are two species found in the Wadden Sea region: Zostera marina and Zostera noltii.