A weird 'alien craft' lying at the bottom of one of the world's oceans is still baffling experts five years after it was uncovered by marine explorers.

Bearing a striking similarity to the spaceship the Millennium Falcon from Star Wars, the sunken UFO, called the 'Baltic Sea Anomaly', was discovered five years ago by Swedish treasure hunters Ocean X team .

A full 91m underwater, the team, led by captain Peter Lindberg and co-researcher Dennis Asberg, spotted it using a used a side-scan sonar.

But the curiosity of extra-terrestrial enthusiasts was piqued when the crew revealed a technology malfunction on their search.

“Anything electric out there, and the satellite phone as well, stopped working when we were above the object,” professional diver Stefan Hogerborn, part of the Ocean X team, said.

“And then when we got away about 200 metres, it turned on again, and when we got back over the object it didn’t work.”

Measuring 61m wide and eight metres tall, the circular-shaped find was suspected of being everything from a giant mushroom, to sunken Russian ship to an alien spaceship , as shown on this Son of Ma Baker video .

And the mystery deepened, as geologist Steve Weiner revealed from his tests that it was not a geological formation - revealing that the structure was created from "metals which nature could not reproduce itself”.

To read more and view the video, click here.