The Gulf of Finland is the easternmost arm of the Baltic Sea. It extends between Finland to the north and Estonia to the south, to Saint Petersburg in Russia to the east, where the river Neva drains into it. Other major cities around the gulf include Helsinki and Tallinn.

The bottom of the gulf is one of the world's largest ship cemeteries. Because of the low salinity and cold waters, and no shipworms, the ships are relatively well preserved.

In the fall of 1743, 17 Russian warships returning from Finland sank in just 7 hours, and in the summer of 1747, 26 merchant vessels sank within 4 hours near Narva. A record was set in 1721 when during the evacuation of Russian troops from Finland, more than 100 vessels were lost within 3 months, including 64 in a single night.

The ecological condition of the Gulf of Finland, Neva Bay and Neva River is unsatisfactory. There is significant contamination by ions of mercury and copper, organochlorine pesticides, phenols, petroleum products and polycyclic aromatic hydrocarbons.

More Info: en.wikipedia.org