50 Fun Facts About Baltic Sea

How many countries have a coastline on the Baltic Sea?

Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia and Sweden; Belarus, Norway and others lie only in the drainage basin.

The Baltic is the world's largest basin of what kind of water?

Its open surface water is under one percent salt, so drinking it in an emergency would actually hydrate you, unlike ocean water.

Which sea does the Baltic drain into through the Danish Straits?

The three straits are the Øresund, the Great Belt and the Little Belt; from there the water reaches the Skagerrak and the North Sea.

Which artificial waterway, opened in 1895 through Schleswig-Holstein, links the Baltic to the North Sea?

It saves ships about 460 km compared with going round Jutland and averages some 32,000 transits a year, making it one of the busiest artificial waterways on Earth.

What is the northern arm of the Baltic, lying between Sweden and Finland, called?

Its northernmost basin, the Bothnian Bay, is where the sea ice forms first each November and where about two-thirds of fish species are freshwater ones.

Which arm of the Baltic connects the sea to Saint Petersburg?

Russia's tsar put his new capital at the mouth of the Neva at the gulf's eastern end after Sweden's defeat in the Great Northern War.

What is the maximum depth of the Baltic Sea, at the Landsort Deep on the Swedish side?

The average depth is only about 55 m, which is one reason the sea is so easily freshened by river runoff.

Which Roman historian described the 'Suebic Sea' (Mare Suebicum), an early name for the Baltic, in AD 98?

He noted the ice breaking up and floating in spring; Ptolemy preferred 'Sarmatian Ocean' and Jordanes called it the Germanic Sea.

Which 11th-century German chronicler first called it the 'Baltic Sea', likening it to a belt?

The name only became dominant after 1600, and 'the Baltics' for the lands east of the sea dates from the 19th century.

In German, Swedish, Danish and most other Germanic languages the Baltic is called the equivalent of what?

Estonian goes the other way and calls it the West Sea, which is geographically correct for Estonia; Finnish uses 'East Sea' too, probably a relic of Swedish rule.

What did the Vikings call the Baltic, a name meaning 'Eastern Sea' that appears in the Heimskringla?

Saxo Grammaticus recorded an older name, Gandvik, whose '-vik' ending shows the Vikings correctly saw it as a bay of the ocean.

Which fossilised resin has been harvested on the Baltic's south shores since the 12th century?

The richest deposits lie in what are now Poland, Russia's Kaliningrad region and Lithuania.

Which federation of merchant towns, grown from Lübeck, dominated Baltic trade from the 13th to 16th centuries?

Its emblematic ship was the cog, and its trading posts or Kontors in London, Bruges, Bergen and Novgorod enjoyed legal autonomy.

What was the emblematic ship type of the Hansa merchants, depicted on its seals and coats of arms?

By the end of the Middle Ages it gave way to the hulk and then to larger carvel-built ships.

Which Latin phrase named the goal of Poland, Denmark and Sweden's 16th–17th-century wars for control of the sea?

Sweden came closest, and in the 17th century spoke of Mare Nostrum Balticum, 'Our Baltic Sea', though the Dutch dominated the actual trade.

At which castle near Helsingør did Denmark collect its Sound Dues from ships passing through the Øresund?

Dues were also taken at Nyborg on the Great Belt and at Fredericia on the Little Belt; the castle is better known as the Elsinore of Hamlet.

Which Russian ruler founded Saint Petersburg at the mouth of the Neva to secure a Baltic outlet?

Sweden's defeat in the Great Northern War handed Russia the eastern coast, and it stayed the dominant Baltic power thereafter.

In the Crimean War, Russia's Bomarsund fortress was destroyed in which Baltic archipelago?

The Baltic campaign is sometimes called the Åland War; the fleet also bombarded Sveaborg off Helsinki and Kronstadt off St Petersburg.

The January 1945 sinking of which German transport ship remains the worst maritime disaster in history?

Torpedoed by a Soviet submarine while evacuating East Prussia, she took roughly 9,000 people down with her in freezing water.

Which Soviet submarine commander sank the German evacuation ship Gustloff on 30 January 1945?

He shadowed the ship on its seaward side for two hours, then swung round to attack from the landward side where no one expected a submarine.

The ferry MS Estonia sank in September 1994 while sailing between which two cities?

An inquiry found the locks on the bow visor failed, letting water flood the car deck and capsize the ship in minutes.

Why do old wooden wrecks such as the Vasa survive so well on the Baltic seabed?

The Vasa spent 333 years underwater off Stockholm and was raised with a largely intact hull in 1961.

How far did the Swedish warship Vasa get into her maiden voyage in 1628 before she sank?

Top-heavy and unstable, she went down minutes after meeting a wind stronger than a breeze; the inquiry punished nobody.

Since 1720, how many times has the Baltic Sea frozen over entirely, most recently in early 1987?

In a typical winter the Gulfs of Bothnia, Finland and Riga freeze; the whole sea did not freeze even in the severe winter of 2010-11.

Roughly what fraction of the Baltic Sea's surface is ice-covered at an average winter's peak?

The ice peaks in February or March; the northern Bothnian Bay is the first to freeze and the last to thaw, sometimes holding ice into June.

Which two seal species depend on the sea's winter ice, one of them breeding only on it?

Only the ringed seal suffers in ice-poor years, because it feeds its pups exclusively on the ice; the grey seal can breed ashore.

What are the occasional pulses of salty, oxygen-rich North Sea water that flush the deep basins called?

Small ones happen about yearly, but pulses big enough to replace the anoxic water in the deep central basin come only about once a decade.

Approximately what share of the Baltic seafloor is a variable 'dead zone' with almost no oxygen?

Dense salty water sits on the bottom cut off from the air, and bacteria there release hydrogen sulphide; fertiliser runoff has made summer algal blooms worse.

Which is Sweden's largest island, home to the Hanseatic town of Visby?

Visby hosts the political festival Almedalen Week and a Medieval Week each summer; in 1361 Valdemar Atterdag of Denmark invaded and killed some 1,500 local farmers.

Which Danish Baltic island is famous for its round churches and the fortress ruin of Hammershus?

Soviet troops bombed and occupied it in May 1945 and did not leave until April 1946; in 1953 a Polish pilot defected there in a MiG-15.

Which curved sand-dune peninsula, a World Heritage Site, is shared by Lithuania and Russia's Kaliningrad region?

Thomas Mann built a summer house above the lagoon at Nida in 1930 and wrote parts of Joseph and His Brothers there.

The Øresund Bridge connects Malmö with which Danish island?

The tunnel section exists so the crossing does not interfere with flights into Copenhagen Airport, and to keep a clear channel for ships and ice.

What is the name of the artificial island in the middle of the Øresund where the bridge meets the tunnel?

The name means 'Pepper Islet', a joke on its natural neighbour Saltholm, 'Salt Islet'.

After Finland and Sweden joined the Western alliance in 2023 and 2024, commentators nicknamed the Baltic what?

The only non-NATO shoreline left is Russian: the St Petersburg area and the Kaliningrad exclave.

Which gas pipelines on the Baltic seabed were destroyed by underwater explosions in September 2022?

The following year the Balticconnector pipeline and a data cable were damaged by a Hong Kong-flagged container ship, and NATO later launched operation Baltic Sentry.

Which of these major rivers flows into the Baltic Sea?

More than 250 streams feed the sea, including the Oder, Neman, Daugava and Neva; the Elbe and Rhine reach the North Sea instead.

Roughly how many people live in the Baltic Sea's drainage basin?

Poland alone accounts for 45% of them; the basin is about four times the area of the sea itself and nearly half of it is forest.

What do palaeontologists call the great river whose plain occupied the Baltic's site before the ice ages?

Later stages of the sea's history carry names such as the Baltic Ice Lake, the Yoldia Sea and the Littorina Sea.

After the Ice Age lake stage, the Baltic basin passed through a freshwater phase named for which mollusc?

The Ancylus Lake lasted from roughly 10,700 to 9,800 years ago, between the Yoldia Sea and the saltier Littorina Sea.

How salty is the open surface water of the Baltic proper, compared with the ocean average of 3.5%?

The saltiest surface water is in the south-west near the Danish islands; the freshest, around 0.3%, is at the top of the Bothnian Bay.

The Baltic's eastern shore was among the last of Europe to be Christianised, during which campaigns?

Swedes converted Finland in the 12th century and Danes and Germans converted Estonia and Latvia in the early 13th; Lithuania was the last European state to convert.

After WWII, several nations dumped what into the Baltic that fishermen still haul up?

Deteriorating containers leak mustard gas; the Soviet Union, the UK and the US were among the dumpers, and the US still withholds the exact sites.

Which region of Poland gained a Baltic port at Gdynia after 1920, rivalling the Free City of Danzig?

The strip of land gave the reborn Polish state sea access at Germany's expense and became a flashpoint of the 1930s.

In which decade did the Baltic Sea reopen to free trade and travel after the Cold War split it between the blocs?

The border status ended only with the collapse of the Communist regimes; the Baltic states and Poland then joined the EU in May 2004.

Which pirate brotherhood held Sweden's largest island during the era of Baltic piracy?

Piracy was rife from the coasts of Pomerania and Prussia at the time.

How long is the Baltic Sea from end to end, roughly?

It averages 193 km wide, covers about 350,000 square kilometres and has about 8,000 km of coastline.

Which three Danish straits connect the Baltic with the Kattegat?

Denmark once collected Sound Dues at all three, at Kronborg, Nyborg and the narrows of the Little Belt near Middelfart.

According to Saxo Grammaticus, what older Norse name for the sea implied the Vikings saw it as a bay?

The suffix -vik is Old Norse for 'bay', which was geographically accurate for this inlet of the ocean.

The Gulf of Riga lies between the Latvian capital and which Estonian island?

Old Latvian called the gulf 'the Little Sea' and the open Baltic 'the Big Sea'.

What is the approximate surface area of the Baltic Sea?

Its volume is only about 20,000 cubic km, because much of it is shallow.