A sunken Nazi warship has resurfaced in the river Danube following low water levels in the record-breaking European heatwave.The Danube River, which runs through 10 countries from southwestern Germany to the Black Sea, has receded to never-before-seen lows along much of its course, exposing rocks, sandbars and old shipwrecks that have rarely been seen before.One German warship from the Second World War was exposed on the riverbed of the Danube in Prahovo, Serbia, as locals swam nearby to cool off in the heatwave. European Investment Bank says it is among 200 vessels that lie at the bottom of the waterway,...