The Seenotdienst was a German military organization formed within the Luftwaffe to save downed airmen from emergency water landings. The Seenotdienst operated from 1935 to 1945 and was the first organized air-sea rescue service.
The German Seenotdienst operated 14 Heinkel He 59 floatplanes (like this Finnish Air Force example) as well as a variety of fast boats.
Some powerful Dornier Do 24 aircraft were captured in the Netherlands and fitted for rescue, and many more ordered.
Pillau, January 1945. Boats and aircraft of the Seenotdienst helped evacuate thousands of German citizens during the last four months of war.
The Dornier Do 18 was a development of the Do 16 flying boat. It was developed for the Luftwaffe, but Deutsche Luft Hansa received five aircraft and used these for tests between the Azores and the North American continent in 1936 and on their mail route over the South Atlantic from 1937 to 1939.
Dornier Do 18
The Do 18 D-ANHR in 1938.
Dornier Do.18 3-view drawing from L'Aérophile August 1936