In the first spy photographs, an enormous beast reared up out of the Caspian Sea, a metal monster studded with jet engines and spewing a mighty spray of water behind it. The United States called it the Caspian Sea Monster, and that wasn't far from the truth.
In the mid-1960s, the Soviets were testing something they called an ekranoplan, which is essentially a hovercraft. It's a hybrid of a boat and an airplane (which is more generally called a ground effects vehicle), floating on water but with wings to provide lift. At speed, it skims along up to 20 meters above the ocean's surface. The idea was that it would act as a high-speed transport, hauling equipment long distances at airplane speed, but with far greater capacity and fuel efficiency than any cargo plane.
The KM (Корабль-макет) ekranoplan was huge: a 37 meter wingspan, more than 90 meters long, weighing 550 tons. It had ten jet engines. Americans thought the KM stood for Kaspian Monster (the translation is closer to "planned ship"), and the nickname stuck. Footage of this beast undergoing sea trials is truly amazing.
The KM was never put into production – this generation of ekranoplan suffered stability problems and was generally impractical to operate. It was abandoned after a crash in 1980.
However, another, slightly smaller ekranoplan did see service in the Soviet military. The Lun was built in the late 80s. Though smaller than the KM, and with only eight jet engines, it had a longer wingspan (helping the stability problems) and was decidedly more badass. The Lun carried six guided missile launchers. Only one was built, the MD-160, and it was in service through the mid-1990s. Another Lun was under construction for use as a mobile hospital and rescue platform when funding was cut.
Today, the MD-160 sits on a drydock in Kaspiysk, with possible plans to restore it. In fact, you can see it on Google Maps. There's an enormous photo gallery of the derelict vessel at igor113's Livejournal page, which is absolutely worth taking a look at. There's something about that 80s military aesthetic – all that dull gray riveted steel. I call it jetpunk, but I'm not sure if that's really a thing.
Photos: igor113, History Channel.
Sources: Haines, Lester. "In search of the Caspian Sea Monster." The Register.
May, James. "Riding the Caspian Sea Monster." BBC.