as Achtung! Zonengrenze! ("Danger! Zonal border!") or Halt! Hier Zonengrenze ("Stop! The zonal border is here") notified visitors of the presence of the border. Foreign military personnel were restricted from approaching the border to avoid clashes or other unwanted incidents. Signs in English and German provided notifications of the distance to the border to discourage accidental crossings. No such restriction applied to Western civilians, who were free to go up to the border line, and there were no physical obstacles to stop their crossing it. East Germany's sea border The inner German border system also extended along the Baltic coast, dubbed the "blue border" or sea border of the GDR. The coastline was partly fortified along the east side mouth of the river Trave opposite the West German port of Travemünde. Watchtowers, walls and fences stood along the marshy shoreline to deter escape attempts and the water was patrolled by high-speed East German boats. The continuous line of the inner German border ended at the peninsula of Priwall, still belonging to Travemünde, but already on the east side of the Trave. From there to Boltenhagen, along some 15 km of the eastern shore of the Bay of Mecklenburg, the GDR shoreline was part of the restricted-access "protective strip" or Schutzgebiet. Security controls were imposed on the rest of the coast from Boltenhagen to Altwarp on the Polish border, including the whole of the islands of Poel, Rügen, Hiddensee, Usedom and the peninsulas of Darß and Wustrow. The GDR implemented a variety of security measures along its Baltic coastline to hinder escape attempts. Camping and access to boats was severely limited and 27 watchtowers were built along the Baltic coastline. If a suspected escape attempt was spotted, high-speed patrol boats would be dispatched to intercept the fugitives. Armed patrols equipped with powerful mobile searchlights monitored the beaches. Escapees aimed for the western (West German) shore of the Bay of Mecklenburg, a Danish lightship off the port of Gedser, the southern Danish islands of Lolland and Falster, or simply the international shipping lanes in the hope of being picked up by a passing freighter. The Baltic Sea was, however, an extremely dangerous escape route. In all, 189 people are estimated to have died attempting to flee via the Baltic. Some East Germans tried to escape by jumping overboard from East German ships docked in Baltic harbours. So many East Germans attempted to