What may well be a small, one or two-person submarine and mothership has been sighted at a military base in Nampo, North Korea. The small submarines are allegedly meant to conduct suicide attacks on enemy ships, and their appearance could be part of a regular training cycle, or something more sinister.

The ship is tied up alongside other Korean People’s Army Naval Force ships at the port of Nampo. It’s approximately 30 meters (about 98 feet) long.

The vessel features a rectangular-shaped section in the stern that appears lower than the rest of the ship, casting a shadow. Inside that section, about 10 meters long, is a bullet-shaped object perhaps six or seven meters long.

In March 2010, after the of the South Korean Navy warship Cheonan that resulted in the deaths of 46 sailors, the Chosun Ilbo on the existence of “human torpedoes” in the arsenals of North Korea. These “human torpedoes” were reportedly elite combat swimmers trained to operate one or two person mini-submersibles known as SDVs, or SEAL delivery vehicles, to conduct suicide attacks against enemy ships. The “human torpedo” units were allegedly formed after the 2003 invasion of Iraq to repel an attack on North Korea.

The ship visible in Google Earth could be a special forces ship equipped with a well deck for deployment and recovery of a SDV, as judging from the lower, rectangular space in the stern of the ship. Well decks are locations on a ship that can be flooded with seawater, allowing submersibles, boats, or amphibious vehicles parked in them to become buoyant with the incoming seawater and then motor away under their own power.

The blue object parked inside the mystery ship could be the SDV itself. SDVs are so-called “wet” submersibles built to transport frogmen wearing SCUBA gear or other breathing apparatus. Although similar to a miniature submarine, SDVs are limited by the air supply of their divers, giving them a relatively short range. SDVs typically operate from motherships, including submarines and surface ships, that transport them close to the target.

It’s here that a mothership and SDV coincide with North Korea’s interests and more importantly, history of covert operations. For decades, North Korea has conducted seagoing infiltration missions against its neighbors. In September 1996, a North Korean Sang-O (“Shark”) submarine, attempting to collect a team of three secret agents it had sent ashore the previous night, was grounded in South Korean territory. Of the submarine’s 26 spies and crew, 25 were killed in firefights or by their own countrymen. A similar incident took place in 1998, with nine North Koreans killed in a mass murder-suicide after their submarine was captured by South Korea. Pyongyang maintains two types of midget submarines, the and classes.

Nearby Japan has also been the subject of seagoing espionage missions. During the 1970s North Korean agents repeatedly crossed the Sea of Japan in small boats, kidnapping Japanese civilians and returning them to North Korea. In December 2001 the Japan Coast Guard machine-gunned and disguised as a fishing vessel of the coast of Japan.

In the United States and the West, the ship in these satellite images could literally be anything. Plenty of people, private organizations, companies, and other institutions own their own boats, and some of those boats may even operate within the waters of a military base. Private boats are modified all sorts of ways, and as long as they meet Coast Guard regulations, they’re perfectly legal. In the U.S. an image of this sort could be written off as almost anything.

This ship, however, is in North Korea, where everything is controlled by the government. It is in the middle of an active Korean People’s Navy base, and surrounded by warships. To the left and right are , or armed hovercraft, known to carry . The large warship to the east is Pyongyang’s largest known warship, a frigate originally built in the Soviet Union. Small patrol boats with pointed hulls appear tied up next to the Krivak and in drydock nearby.

North Korea is one of the most tightly controlled, repressive societies on Earth. It is also very poor, with a per capita income of just $1,197, . There are few very, very few individuals wealthy enough to embark upon vanity shipbuilding projects. Most privately owned vessels in North Korea are likely fishing boats, and this is no fishing boat, nor would one berth among a collection of the country’s most powerful warships.

The ship in Nampo is almost certainly a military-owned vessel with a specific purpose. One possible explanation is that it is a special forces ship, designed to ferry frogmen to a drop-off point, whereupon they will proceed to their destination in a SEAL delivery vehicle, or mini-submarine. There the frogmen would then conduct a variety of missions, including suicide attacks using explosives.

North Korea has a large number of special forces troops, and Pyongyang maintains an active duty military of approximately 945,000 including . Two brigades are assigned to the Korean People’s Navy and serve in the role of marine infantry and naval special forces. The Reconnaissance General Bureau, North Korea’s intelligence agency, also maintains a battalion of agents, and submarines, for out-of-country operations.

In addition to infiltration boats and submarines, North Korea also has a number of , or SILCs. SILCs are basically speedboats fitted with enclosed cabins and ballast tanks that, once filled with seawater, allow the boat to ride lower on the surface of the water to evade detection. Pyongyang has clearly invested in a variety of vessels for seaborne infiltration and a SDV would just be one more tool in the Kim family’s toolbox.

Of course, all of this is just informed speculation. If blurry images are enough to prove the existence of something, Bigfoot would have been proven real a long time ago. The ship in Nampo could be something else—something likely military—perhaps with an even more interesting purpose. We just don’t know. But it’s quite clear from the country’s history that if it didn’t have a SDV fleet, it would certainly like one.

One question the ship sighting raises: if this is a SDV and mother ship, does it actually mean anything? North and South Korea are experiencing a thaw in relations, and even U.S. President Donald Trump reportedly “” North Korean leader Kim Jong-un. North Korea has not staged any major military provocations . That having been said, in August 2017 Trump previously on North Korea if it attacked the United States with nuclear weapons. North Korea’s “human torpedoes” could have been conducting typical training, or they could have been preparing to counter a U.S. attack during yet another invasion scare.

The presence of this unusual ship in Nampo is another mystery unearthed by open source intelligence enthusiasts, often sitting bleary eyed at some late hour of the day, a hostile country scrolling across the computer screen with a tantalizing lack of detail. Something catches the eye and down the rabbit hole you go.

Is this ship a miniature submersible designed to allow a frogman to blow himself up and take a Yankee warship with him? Is it something else entirely?

We may someday know—but not today.