The first marked Luftwaffe air sea rescue aircraft was forced down, by Spitfires of 54 Squadron, before the official BoB. This was an He 59. It was unarmed and its crew were registered with the Red Cross. They had already rescued both German and British airmen off the Norwegian coast. Why then did the RAF continue to engage these aircraft?
Dowding wrote an explanation in 1941:
"Throughout the Battle [of Britain] of course, fighting continually occurred over the sea, and German aircraft, damaged over England, had to return across the Straits of Dover or over the English Channel. Far more German than British crews fell into the sea. The Germans therefore developed an elaborate system of sea rescue. Their bombers had inflatable rubber dinghies, and various other rescue devices were adopted. Crews were provided with bags of a chemical known as fluorescein, a small quantity of which stained a large area of water a vivid green. Floating refuges with provisions and wireless sets were anchored off the French coast. 'E Boats' and rescue launches were extensively employed, and white painted float planes, marked with the Red Cross, were used even in the midst of battle. We had to make it known to the Germans that we could not countenance the use of the Red Cross in this manner. They were engaged in rescuing combatants and taking them back to fight again, and they were also in a position, if granted immunity, to make valuable reconnaissance reports. In spite of this, surviving crews of these aircraft appeared to be surprised and aggrieved at being shot down."
So Dowding did some grim arithmetic. Because relatively few British airmen were going into the sea and because if rescued, unlike their German counterparts they would not be returned to combat but become prisoners of war, he was not prepared to allow the Luftwaffe's air sea rescue service aircraft to freely operate to rescue anyone. It was better to lose a few of his own than allow the repatriation of many more of the enemy's.
The Germans vehemently denied that these aircraft ever undertook any sort of reconnaissance missions and there is little if any evidence to support the contention that they did. Even Dowding only raises the possibility, not actually accusing them of doing so.
Cheers
Steve