Divers working for the World Wide Fund for Nature (WWF) to remove fishing nets abandoned in the Baltic Sea caught a bigger fish than they expected: a World War II Enigma machine. It was on the seabed ensnared in a ghost net. The diver who first spotted it thought it was an old typewriter, but his colleague, underwater archaeologist Florian Huber, immediately suspected from the description that it was an Enigma machine. People don’t usually toss old typewriters overboard in the middle of the Baltic, while Enigmas were used by the German navy and certainly went down with ships and submarines. Two weeks later the two returned to the find site together and Huber confirmed that it was indeed an Enigma machine.

It was found on the bottom of Geltinger Bay where dozens of German U-boats were deliberately sunk by the German Navy in May of 1945. This machine is an M3 model with three rotors, so it must have come from a warship rather than a submarine as the U-boats were equipped with four-rotor M4 machines. The nameplate has yet to be deciphered. It won’t baldly state the name of the vessel it was on, but it will provide a clue to its history.

The Enigma enciphering machine was used by the German military to create and receive coded messages before and during the war. It used a system of rotors, lamps and plugboards to scramble text that would then be unscrambled by a receiving machine calibrated to the same settings — wheel order, rotor positions, plugboard connections — as the originating machine. The sequences were changed daily. The Polish Cipher Bureau was able to figure out the method of encryption before the war, but it was the codebreakers at Bletchley Park in Milton Keynes, especially mathematician Alan Turing, who finally broke Enigma in 1941. German forces kept adding rotors, plugs and lamps, increasing the level of difficulty, but they never realized that the Allies, armed with Colossus computers capable of calculating the daily key settings, could read their encrypted messages.

Engima machines were produced in large quantities throughout the war. Approximately 100,000 of the machines were deployed, but most of them were discarded or destroyed. Today it’s rare to find an Enigma machine that is entirely original. The ones in museums are often Frankensteined together from several incomplete machines.

The divers have reported the find to the Schleswig-Holstein State Office for Archeology which will study and conserve the Enigma for eventual display. The desalination process alone will take a year.