The Turkish navy found a WWII German submarine that sank in the waters of the Black Sea and will showcase its discovery in a new documentary film. According to the television channel Russia Today, the U-23 submarine was found at a depth of 40 meters and about 4 kilometers off the shore of the resort town of Agva, near Istanbul.

U-23 was one of a series of six German submarines set to attack Soviet ships on the Black Sea. According to the report, researchers discovered the U-20 – another U-boat from the same fleet – off the coast of northern Turkey in 2008.

Turkish newspaper Daily Sabah says the submarines participated in 56 operations against Soviet ships in the Black Sea, and according to Russia Today, they succeeded in sinking dozens of ships. By 1944, three of the fleet of six had been sunken by the Soviets.

In 1944, Germany ordered the crew of the three remaining U-boats to scuttle the ships to keep them from falling into Soviet hands, earning them the nickname "Hitler's lost fleet."

Since the end of the war, many have sought to locate the six submarines. Only one of them remains missing: The U-19, which is thought to lie on the seafloor off the coast of Zonguldak, Turkey, to the east of where U-23 was discovered. Researchers estimate that U-19 lies at a depth of about 455 meters.

Hakan Aslan, the director of the documentary, titled "Mavi Tutku" ("Blue Passion"), told Daily Sabah that the film is expected to premiere soon. "We have been working on German submarines' operations in the Black Sea for a long time," he said.

The submarine was discovered by the crew of rescue and towing ship TCG AKIN, which according to Daily Sabah was introduced into the Turkish fleet last year. The newspaper reported that the TCG AKIN is equipped with deep sea cameras that can function at depths of up to a kilometer. The commander of the TCG AKIN Cenk Ilgun expressed his happiness with the discovery, saying that the submarine was an important witness to an important era in history.