Channels to Mandø The seabed around Mandø is subject to constant changes due to sand migration. There are two buoyed channels which lead to Mandø S, one from Gydeløbet in W and one from Østerdyb in E. The buoyage of the two channels is established 1.5.-15.11. Only the channel from Østerdyb is shown in the chart. It is not recommended to use either of the buoyed channels without local knowledge.