BERCK-SUR-MER, France—Some 30 migrants whose dinghy capsized in the English channel as they tried to reach Britain were rescued on Friday, while one man who was on board died, French authorities said. A coast guard vessel reached the dinghy, which had set off from a beach near Calais, northern France, in the middle of the night, and was able to rescue most of those on board. But one of the migrants, a young man from Sudan, was dead in the water, according to local Deputy Prefect Frederic Sampson. The man died from hypothermia, amid temperatures between -1 and -3 degrees Celsius (between 30 and  26.5 degrees Fahrenheit) on the open sea. Once brought back to shore by rescuers, the survivors—some of whom wore flip flops and carried their belongings in plastic trash bags—boarded a large white coach to be sent to temporary housing in the region. They were flanked by …