I believe I can definitely explain what the OceanExplorer.se team has found on the floor of the Baltic.
My explanation is based on information that is available on the OceanExplorer.se, and other news websites.
According to the OceanExplorer.se website the mystery is as follows:
On
June 19th the Swedish-based diving company Ocean Explorer discovered something
they’ve never quite seen before. They were exploring in the Baltic Sea between
Sweden and Finland looking for sunken treasures when a very unusual image
suddenly appeared on the sonar. A 197 feet diameter cylinder shaped object
was discovered at the depth of approximately 275 feet.
Several websites have repeated the claims that it is 197 feet (approximately 60m in diameter). But why is the size of the object so important?
The first question to answer is, if the object is man-made or not. The size is very important in determining this.
The site claims the object is 60m wide – but there is no scale on the images provided, so we have to trust the claims of the Ocean X team.
You can see a better picture of the above (minus the scale) at the following website:
http://www.earthfiles.com/news.php?ID=1963&category=Environment
According to Peter Lundberg, a second object is “600 feet away” from the first. Seeing both objects together in the same image allows us a better opportunity to judge scale.
By the scale shown the picture, the second object is 13 units from the first. 600 feet/13= 46 feet per line. Judging from the picture, the object is actually about 2 1/4 units wide. To be 200 feet wide, it would need to be 5 units wide, not 2 1/4.
At approximately 103 feet wide, we have to consider that this is one of 19th Century Russia’s round warships called a “Popofkas”, that operated in the Baltic sea until the early 20th Century:
http://www.cityofart.net/bship/ru_novgorod.html
Popofkas were warships designed for shore bombardment with a circular hull, 101 feet in diameter.
Based on the evidence, it seems clear that the Ocean X team has found an interesting and probably very unique find – but certainly no UFO.