In the Yamalo-Nenets Autonomous Okrug in Russia you can see many swamps. In one of these swamps there is still
Mi-6 helicopter in 1981 fell into a swamp nearcity of Tarko-Sale. Prior to that, he flew across the expanses of the USSR for almost 17 years. It is believed that the crash occurred due to the failure of both power units. Literally a few minutes before this, the aircraft replenished its fuel reserves.
Before the crash itself, the helicopter flew at a low altitude, as it was carrying cargo on an external sling. After the failure of the power units, the pilots decided to land somewhere in the swamps.
Fortunately, everyone in the helicopter managed to survive. But the ship itself, due to a strong blow, was no longer subject to restoration.
After an investigation, it turned out that the reason for the failure of the engines was the ingress of water into the vessel's tank. This happened due to the fact that someone, without the knowledge of the pilots, pumped water into the wrong tanks.
The helicopter was not evacuated for two reasons. First – inaccessibility of the area. Second – swampiness. Therefore, they simply took everything they needed from the ship and left it in the swamp.