German research divers recently looking for abandoned fishing nets along the Baltic seafloor that threaten marine life, found a rare piece of history: an Enigma machine — the German encryption device used by Nazi forces to send secret message during World War II.

Designed shortly after WWI by the engineer Arthur Scherbius for commercial usage, the cipher engine was adopted by many national governments and militaries.

RELATED: A closer look at Enigma machines, and ones sold at auction.

The device was found off the coast of northeast Germany in the Bay of Gelting, which is part of the Baltic Sea, after Submaris — a company based in Kiel — used side-viewing sonar technology to identify the net that it was caught in.

“A colleague swam up and said: ‘There’s a net there with an old typewriter in it,’” Submaris lead diver Florian Huber told the DPA news agency.

Rusted and a bit overgrown with orange algae, the machine, and was still recognizable as an Enigma.

Research diver Florian Huber discovers the Enigma machine at the bottom of the Baltic Sea.

Research diver Florian Huber discovers the Enigma machine at the bottom of the Baltic Sea.

The find was a discovery like no other, said Gabriele Dederer of the World Wide Fund for Nature, which hired the divers for the marine conservation effort.

Abandoned or lost fishing nets, known as ghost nets, represent a deadly trap for fish, marine mammals and sea birds — and are a form of underwater pollution.

“We regularly find larger objects, on which the nets get tangled underwater. Such so-called ‘hook points’ are often tree trunks or stones,” Dederer said. “The Enigma is by far the most exciting historic find.”

Florian Huber at the archaeological office of Schleswig-Holstein, which will study the Enigma cipher machine.

Florian Huber at the archaeological office of Schleswig-Holstein, which will study the Enigma cipher machine.

Huber said that the machine was most likely sent to its watery resting place in May 1945. That month saw 47 German U-boats scuttled in Gelting Bay by their crews, who were determined not to let the vessels fall into the hands of the Allies.

“We suspect that our Enigma went overboard in the course of this event,” Huber said.

“As an underwater archaeologist, I have already made many exciting and strange finds,” Huber said. ‘However, I didn’t dream that we would once find an Enigma machine. It was a gray November day I will not forget so soon.”

The Enigma machine has now been sent to Museum of Archaeology in Schleswig, where it will be preserved and studied further.