The Baltic Sea Anomaly refers to interpretations of an indistinct sonar image taken in June 2011 by Peter Lindberg, Dennis Åsberg, and their Swedish treasure hunter group named “Ocean X.” It was discovered on the floor of the Northern Baltic Sea at the center of the Bothnian Sea. For its strange appearance, the Baltic Sea Anomaly has caused debates on what it could be.

The Baltic Sea Anomaly is a still-unknown object deep in the Baltic Sea, which, some say, could be a pre-Ice Age artifact or Nazi anti-submarine device. Oddly, divers’ electrical equipment stops functioning within 650 feet of its location, and a strong radio signal has been detected coming from this sea-bed area.

The “Ocean X” team has claimed their image shows a 60-meter diameter circular object with features resembling ramps, stairways, drag marks, and other structures, which indicates it was not naturally created.

Some experts, especially the ufologists community, have claimed that the Baltic Sea Anomaly is the wreck of an alien ship that was somehow sunk in ancient times. At the same time, the mainstream researchers consider it to be nothing more than a natural rock formation.

The divers who discovered the anomaly deep into the ocean gave samples of stone from the object to Volker Brüchert, an associate professor of geology at Stockholm University. Swedish tabloids quote Brüchert as saying: “I was surprised when I researched the material I found a great black stone that could be a volcanic rock. I hypothesize that this object, this structure, was formed during the Ice Age many thousands of years ago.”

In other words, an expert appears to back up their claims that this seafloor object is unexplained and perhaps is an Atlantis-like ancient building complex.

On the other hand, several imaginative illustrations resembling underwater photos or high-resolution scans have been circulating through various news-media sources, along with claims that “the object could be a UFO, or a portal into another world, or an underwater Stonehenge.” To this day, there is no conclusive explanation for the existence of the strange Baltic Sea Anomaly.

Apart from the Baltic Sea Anomaly, a lot of complicated ancient underwater structures have been discovered that are widely believed to be ruins of artificial things or evidence of lost civilizations. The Yonaguni Submarine Ruins situated in Japan is significantly one of them. Another one is the Underwater Structure of Cuba.