Baltic Naval Actions

Väinämöinen, sister ship to Ilmarinen

Most of the naval action in the Baltic up until 1944 was mainly concerned with the laying of defensive minefields by both the Germans and the Finns in the eastern part of the Baltic Sea.
For further information about the above my I recommend that you try and get hold of the following book "German Destroyers of World War Two", by M J Whitley. This gives invaluable information with regard to the naval war in the Baltic that was carried out by German destroyers and torpedo boats from 1941 - 1944. 

Also, I can recommend the following for additional information about operations in the Eastern Baltic, "German Coastal Forces in World War II" and "German Cruisers of World War II", also by M J Whitley. 

The minefields laid by the Germans and Finns at the entrance of and across the Gulf of Finland that Bob mentioned had the effect that for nearly three years the Soviet Baltic Fleet was kept bottled up and made useless at its base of Kronstadt outside of Leningrad. A few Soviet submarines were able to get through the minefields and anti-sub barriers to attack German supply shipping to ports in Latvia and Estonia, but most of them didn't make it back to port having been sunk by German anti-sub chasers. It wasn't until the siege of Leningrad was lifted in early 1944 and Heeresgruppe Nord had to withdraw to the Dvina line that light Soviet naval vessels could venture out into the Baltic and try to intercept German convoys to Windau and Libau in Latvia which they did with some success, though also suffering losses in encounters with German Navy forces.

Many if not most of the supplies for Heeresgruppe Nord at the Leningrad front (later Kurland pocket) were shipped by sea to ports such as Reval, Libau and Windau. Most of these convoys got there without being bothered by the Red Fleet except for attacks by the Red Air Force which lost a lot of planes trying (those Kriegsmarine AA gunners were pretty good).

As mentioned the large minefields limited (nearly stopped) the actions of the great Red Baltic Fleet during 1941-44 period. Germans were anyway pretty worried about the massive fleet (it was a big one indeed, especially it's sub arm) and feared it could break to the Baltic when Leningrad was seriously threatened. Germans intended to force soviet main fleet to the sea by heavy bombing and destroy escaping vessels by their own task force (lead by just commissioned Tirpiz with Prinz Eugen, Lutzow several other ships if I remember right). German TF eventually set sail and cruised in northern Baltic - but the Red Fleet did not, as the air attacks caused heavy damage to many soviet major ships and crippled one battleship. Don't know if the soviets ever thought about setting sail, though. Anyway, if only in paper, there was a possibility of a major surface action in the Baltic. 

Mines caused anyway huge damage to the Baltic fleet, sinking several destroyers, damaging more destroyers and cruisers (as did Finnish coastal defences during Winter War) and destroying a heap of subs and light units. Also many German ones were victims, as well as the armoured coastal battleship, Finnish flagship Ilmarinen.