Nazi German warships scuttled in the Danube River during the Second World War are resurfacing as water levels plunge — a striking sign of the extreme heat and drought gripping Europe this summer. The sweltering heat has contributed to devastating wildfires and pushed water levels in vital waterways, including the Danube, to record lows. (Darko Vojinovic/The Associated Press)But the extremely low water levels have raised much more urgent concerns for several countries along Europe's second-longest river. Much of eastern Europe, including areas of the Danube River basin, was also much warmer than average. Two of the German warship wrecks that have emerged in the stretch of the Danube river in Serbia.