The Baltic sees little action in 1901. The German fleet sails there only 1.3% of the time in the spring, though in the fall Russia's northern fleet will occasionally ply these waters if the Tsar feels certain that Germany intends to bounce him out of Sweden.
There is really only one German opening that justifies sending the fleet into open waters - The Baltic Opening (A Ber-Kie, A Mun-Ruh, F Kie-Bal). Barring English interference, Holland and Denmark will fall under the Kaiser's control and Sweden will be denied the to the Russian. And the Czar's option of moving to the Baltic is gone, as such a move would give Germany the extra build of Sweden because there is an army following up to enter Denmark.
- The Scribe
You will rarely see fleets entering the Baltic Sea in the begining of the game, but if Russia, Germany and England can't agree about how to devide scandinavia between them than it is the best place to have influence in Sweden, Denmark and the north of Germany, or start attacks on Russia/Germany.
The "all-out-Russian-attack" of Germany involves the moves MUN -
SIL, BER - PRU and Fleet KIE - BAL.
(Unfortunately, this opening is rarely seen nowadays)
Germany: The remote Baltic is a useful place for Germany's 2nd Fleet. First trick Russia by building in Kiel, moving to Baltic instead of Heligoland. Combined with forces in Denmark and Northern Germany, Baltic Sea is the German springboard for Sweden and Livonia (Russia itself). A German fleet in Baltic also helps diplomacy with England.
Russia: Russia rarely goes for the Baltic unless she is concentrating exclusively on Germany, and supremely confident in Scandinavia.
The interesting about the Baltic Sea/Gulf of Bothnia area is that it is a kind of northern Adriatic; remote. If you get there first you own the place.