In 1935, German scientists set up a laboratory on the roof of the Charite Hospital in Berlin in order to study ball-lightning (German: "Kugelblitz"). Apparently the atmosphere inside ball lightning is not of this Earth. Their thinking was that if stable imitation ball-lightnings could be created (plasmoids) it might be possible to fit an aircraft or submarine inside them which would then be invulnerable. Nothing would be able to collapse such a plasmoid except a radio signal on the planned frequency from the operators.
It seems to be a scientific fact that such an artificial stable plasmoid cannot be developed in any laboratory on Earth because of the energy requirement. However that may be, there are some signs that towards the end of the war the Germans had managed to create such a plasmoid and put inside it a flying machine the size of a basketball. They called the whole thing "der Kugelblitz".
After the war German research was continued at two laboratories in Argentina. On 31 January 1960 two submarines of unknown flag were detected entering Golfo Nuevo on the South Atlantic coast of Argentina, and for the next three weeks numerous Argentine Navy attacks against them were made by gunnery, homing torpedoes, aerial homing torpeoes and depth charges, most of it using sophisticated US anti-submarine warfare material. After about three weeks the intruder U-boats, having never returned fire, left of their own accord undamaged.
Foreign naval observers identified the submarines as "Type XXI German U-boats of the Second World War." Many thousands of photos of these boats were taken in the Gulf and ashore but all exposures turned out hopelessly blurred and so no photo exists. Because of this problem Argentine naval crews were issued with sketch pads and pencils before sailing and told to draw impressions of what they saw.
I was given an interview in Buenos Aires at Easter 2013 with a naval intelligence officer who had been aboard one of the Argentina warships at the time. He confirmed about the photos but would not be drawn on any other details of the operation. He has also written a book in which a chapter of about fifty pages is devoted to the various attacks made against these U-boats.
The next time we have news of one of them comes is an innocent mention in private correspondence. Alejandro Diograzia did his national service for Argentina as a signaller at the Las Leones lighthouse, near Camarones, between 1959 and 1961. In contemporary letters in 1960 to his aunts he mentioned that German U-boats of the Type XXI called at the lighthouse on several occasions. The visits would coincide with strange encrypted radio messages. Diograzia stated that the crewmen all looked about forty years old which would make them in their mid-twenties when the Second World War ended. (See blog "German Diograzia Escritor").
In recent times the lighthouse (in service from 1917 to 1968) was abandoned due to difficulties in landing men and supplies. As late as 1967 there were instances of residents and tourists calling the coastguard after seeing such submarines inshore, often partially beached. It would usually take the Argentine Navy about a week to send a ship (never an aircraft) to investigate.
In this area there is an great island chain discovered by the Spaniards shown in maps over the centuries. Several hundred years ago the islands dematerialized and have not been seen since. In the 1990's I spoke to various men who had been seamen aboard Argentine ELMA line ships during the war. They were prepared to state that they sometimes took supplies to meeting points with U-boats near three islands well offshore "which appear on no maps" but none would give an indication of the position of these islands.