Baltic Sea: Advantages: St. Petersburg and Kaliningrad are both industrial areas, located in the heart of Europe. Disadvantages: The Baltic Sea is controlled by Germany and Denmark, and the Nordic countries have a bad attitude towards Russia.
Black Sea: Advantages, ice-free port, convenient transportation in Ukraine and Caucasus. Disadvantages: Turkey is stuck in the waterway and the water is shallow.
Pacific Ocean: Advantage, the freezing period is not long, so trans-siberian railway can be used for bad luck. Disadvantages: it is separated from the core of Russia and Europe by Siberia, and the first island chain of the United States is mainly deployed here.