The baltic, especially in its northern and more deeper regions, is the perfect sea for wrecks.
Remember the salvage of the Wasa. Wood does not decompose there as quickly as in other seas and most damage to wrecks is actually done by human interference (nets, anchors, deliberate demolition, wartime depth charges etc) instead of worms or bacteria or currents.
Here's a pic of a 18th century sailing vessel, a two masted brig or brigantine which was simply sitting upright at the bottom with its masts still intact in around 100 meters of water. It simply looked as if somebody had parked it there and forgotten it for over 200 years. Such a find is important because there's actually little known about everyday small merchant craft of that era. Plans for warships have been preserved in state archives, but not for such smaller vessels.
The greatest concern for this wreck is that some moron will simply demolish it by accident.
http://www.abc.se/~m10354/uwa/
Here's a homepage with a lot of baltic wrecks