Potentially explosive echoes of the history Record-low water levels in the Danube, caused the summer super heat have transformed Europe's 2nd-longest waterway into a vast half-submerged archaeological and historical excavation site. The locals found wrecks of dozens of #Nazi German naval gunboats that have surfaced along the Serbian-Romanian border, particularly near the port city of Prahovo. In total there are around 200 of those boats hidden in the river.