Before the war, the Germans realized that British bomber attacks would come from the sea and it was inevitable that air combat would take place over the freezing waters of the North Sea. In cold water (10C), humans can survive for 2 hours (assuming they have a life jacket).

Therefore, in 1935, the Luftwaffe set up an air-sea rescue organization (Seenotdienst) to rescue aircrews in the North Sea and Baltic Sea. They selected the Heinkel He 59 for this purpose (other aircraft were later added).
The He 59 was unarmed, sported civilian markings, and was painted white with conspicuous red crosses (see picture).

The first combined air-sea rescue operation occurred on 18 December 1939, when British Wellington bombers attempted an attack on German warships off Wilhelmshaven.

German defenders shot down several bombers and some 20 British aircrews were rescued from the icy waters.

When the Luftwaffe started to prepare for the Battle of Britain they expanded the organization to cover the English Channel.

On 1 July 1940, the RAF's 72 Squadron shot down Leutnant Fehske's He 59 near a convoy off Tyneside. The Germans protested, but the British declared their intention to prevent the Germans from saving the lives of their valuable crews, making this decision an official policy.

After further attacks, the Germans armed and camouflaged their rescue aircraft. On 20 July, one of the float planes shot down a Hurricane from 43 Squadron.
Despite these attacks, the Germans continued their rescue operations (sometimes with escort) and from 1 July to 6 October 1940, the Seenotdienst rescued more than 100 men (including some British) at the cost of 22 aircraft and 49 casualties.

Some weeks after the start of the Battle of Britain, the British implemented their own air-sea rescue organization.

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