English: A schematic of the water surface level changes with the tides. Average low water spring or average low water neap tide; used as a reference, which one is used depends on whether LWN or LWS is lowest. The schematic was hand drawn based on an image from the book "Leidraad voor het Stuurbrevet" by Richard Vooren, Paul Van den Keybus. Note that the ALWS/ALWN is best replaced by LAT (lowest astronomical tide) in a next version of the image. As this water level may be lower than ALWN/ALWS, some of the text will be rendered obsolete