At the height of the Cold War in the 1960s, CIA analysts spotted a mystery vehicle being developed on the Caspian coastline of Soviet Russia. The craft was dubbed the “Caspian Sea Monster” and was eventually revealed to be an “ekranoplan,” a naval vessel that skims above the waves at jet aircraft speed.

Decades on from the collapse of the Soviet Union and that country’s ekranoplan project, photos from China indicate Beijing may now be pursuing its own such development on the Bohai Sea. The vessel has been dubbed, predictably, the Bohai Sea Monster.

Military aviation expert Justin Bronk told RFE/RL that China’s apparent development of the experimental vessel highlights Beijing’s willingness to try nearly anything in the pursuit of tactical advantages over its rivals and enemies.

“China is notable in its willingness to fund and test large numbers of different technical and technological solutions for military problem sets,” Bronk, a senior research fellow at the Royal United Services Institute says, adding that even designs with a low chance of success are being developed by the Chinese.

“Presumably based on the logic that a few at least will prove to be unexpectedly useful and successful,” he says.

Ekranoplans offer some advantages over both aircraft and ships. The low-flying vessels would remain hidden to most radar systems until appearing over the horizon. With top speeds around 10 times faster than that of naval ships, a fleet of incoming ekranoplans would give coastal defenses precious little time to react. Ekranoplans are also able to pass harmlessly over anti-ship mines and can carry heavier loads than equivalent aircraft thanks to the ground effect cushion on which they surf.

Those advantages recently sparked the imaginations of engineers at DARPA, America’s military development agency, which spent a reported $22 million to develop designs for a “Liberty Lifter” craft which would fly mostly in ground effect.

In June 2025, the American program was ended early.

A spokesman for one of the companies involved told the Airforce Times that “through the Liberty Lifter program, we were able to show the viability of the design and the feasibility of novel manufacturing techniques.” But nothing beyond artist’s drawings of the American craft have been seen.

Now leaks from China, either planned or organic, indicate Beijing has reached the prototype testing phase of its own ground effect vehicle.

There is no hard evidence the vessel spotted on the Bohai Sea is a military project, but its battleship grey color scheme and a large cargo door has led experts to speculate it could be intended as some form of naval logistics vessel.

“The niche that an Ekranoplan might be developed to fill in the [Chinese Navy] would be a capacity to move cargo that is too heavy for even large transport aircraft, far faster than traditional ships could,” Bronk says. “In theory this could be useful for China’s capacity to reinforce disputed small islands rapidly with significant numbers of anti-ship and air defense missile systems.”

Previous Ekranoplan designs have been hampered by the immense power needed to become airborne, which can offset the fuel efficiency of flying in ground effect, as well as their slow turning arc. Additionally, flying just above sea level puts the vessels at increased risk of bird strikes compared to aircraft that cruise at high altitudes.

China’s navy is currently undergoing rapid expansion, with the authoritarian Asian country reportedly aiming to build a fleet of six aircraft carriers by the 2030s. Recent images of unusual landing craft have heightened fears Beijing is actively preparing for a potential invasion of Taiwan.