The 26 meter long passenger ferry Altona went aground on the Elbe River.   The Altona was headed to Neuenfelde from Blankenese with 30 passengers when the vessel became stuck in the mud at low tide.   Four passengers were safely taken ashore by the DLRG.  The remaining passengers remained on board for several hours until the rising tide returned.   The Altona proceeded to the nearby pier.   No reports of injuries, damage or pollution being released.