From a distance, the Baltic looks familiar, doesn’t it? But the moment you step away from the promenade and give yourself a little quiet, you start to notice something more. This sea keeps surprising you – with its history, climate, underwater secrets and wildlife that people rarely talk about. So before you point your deckchair at the sun again, have a read. Because the Baltic can be far more fascinating than it seems at first glance.
One of the world’s youngest seas? Yes – it’s the Baltic! A surprising Baltic Sea fact
Not everyone realises that the Baltic Sea is one of the youngest seas on Earth. It was formed relatively recently, around 12–15 thousand years ago, just after the end of the last ice age. On a geological timescale, that’s barely a moment. Earlier, the area where the Baltic now stretches was covered with ice or held vast bodies of freshwater.
The formation of the Baltic went through several stages. At first, there was a glacial lake, later the so-called Yoldia Sea, and only then did marine waters start flowing in from the west. Today’s shape of the Baltic is the result of thousands of years of climate change, erosion, crustal movements and the constant mix of salt and freshwater. All this makes the Baltic truly unique – very different from most seas in the world.
If you’ve ever wondered why the sea where you spend your holidays sometimes behaves a bit like a lake, now you know – it’s the geological “memory” of its very young past. And it’s exactly this youth that makes the Baltic so intriguing and worth discovering in a way that goes beyond just lying on the beach.
Why does the water in the Baltic feel so “soft”? Baltic Sea facts you probably didn’t know
The Baltic is one of the least salty seas in the world. Its salinity averages around 7‰ (parts per thousand), which means there are only about 7 grams of salt in a litre of water. For comparison, the Mediterranean Sea reaches up to 38‰. In practice, this means that Baltic water is much gentler on your skin and doesn’t sting your eyes like ocean water does.
This level of salinity is the result of several factors. More than 250 rivers flow into the Baltic, bringing in huge amounts of freshwater. On top of that, the Baltic has very limited water exchange with the North Sea – the Danish straits are too shallow and narrow to allow a strong flow.
This unique chemistry shapes the Baltic’s ecosystem. You won’t find coral reefs here, but you will find species that have adapted to these conditions – such as Baltic herring, local cod populations or eel. Low salinity is also why children can safely splash around here, sometimes even with their eyes open, without tears.
When the Baltic was… a lake. A fascinating Baltic Sea fact from thousands of years ago
This is not a myth or a sailor’s tale. In the Baltic’s history there were times when it was cut off from the ocean and turned into a gigantic lake. That’s what happened during the Ancylus Lake phase, when sea level dropped and contact with the North Sea was temporarily broken. The entire area became a freshwater basin with a slightly different climate and a completely different flora and fauna.
Modern geological research confirms these changes – in both sediment analysis and the shape of the coastline. What’s more, scientists suggest that if the exchange of waters between the Baltic and the North Sea were interrupted again, for example due to climate change or human interference with the straits, the Baltic could once more become a lake.
This is more than just theory. The Baltic is shallow, semi-enclosed and very sensitive to change, which is why its geographical status is such a hot research topic. It’s an interesting thought to walk along the shore knowing that once upon a time there might not have been a drop of saltwater there.
An underwater museum of history – Baltic Sea facts that fascinate divers
If you love history, the Baltic Sea will captivate you not only from the shore. On its seabed lie thousands of shipwrecks, from medieval merchant vessels to warships from World War II. For centuries, the Baltic was a key trade route and a strategic area for many navies, which left behind countless underwater traces.
What sets these wrecks apart is their remarkable state of preservation. Because of the low salinity and the lack of many wood-boring organisms, a lot of the structures remain almost intact. For divers, it’s a real paradise – you can see hulls, gun mounts, and sometimes even remnants of cargo.
Examples? The wreck of the ferry “Estonia”, the German battleship “Gneisenau”, and dozens of smaller merchant ships. The bottom of the Baltic is like an informal underwater museum, attracting not only history buffs but also researchers from all over Europe. Many of these sites can be visited legally as part of organised diving trips.
How many islands does the Baltic have – and which is the largest? A Baltic fact that might surprise you
Most people picture the Baltic as all beaches and cliffs, but its islands are just as interesting. In the Polish coastal zone alone we have the well-known Wolin, Usedom and Sobieszewo, but that’s only the beginning. Across the whole Baltic there are dozens of islands and islets of various sizes and character.
The largest Baltic island is Gotland, belonging to Sweden. It covers over 3,000 km², making it not only the biggest, but also one of the most important in terms of tourism and culture. Gotland has a long history dating back to the Viking age and is now famous for its atmospheric towns and well-preserved heritage.
We should also mention the Danish island of Bornholm and the Åland archipelago, belonging to Finland. These islands offer mild climates, green landscapes and excellent infrastructure for cyclists and hikers. They’re a great choice if you want to see a completely different face of the Baltic – one without windbreaks and crowded promenades.
Storms for a month and a half? Baltic Sea facts that change how you see the weather
You hear “Baltic” and think: holidays, beach, windbreak, sunshine. But the weather at the Polish seaside can be full of surprises – and not only in July. The Baltic is a stormy sea, and it shows its power most clearly in autumn and winter. In some parts of the sea, storm conditions can last for 45–55 days a year. That means that for a month and a half, waves reach impressive heights and the wind quickly chases away anyone dreaming of a calm November walk along the shore.
Importantly, these storms are not rare. They’re a natural part of the sea’s hydrological cycle. And although in summer the Baltic often seems calm, just a few days of low-pressure weather can change everything. It’s storms that shape the coastline – they strip sand from one beach and pile it onto another. Sometimes they damage piers, reshape cliffs, and above all… remind us that the Baltic is a wild sea that can be very unpredictable.
So if you’re planning a seaside holiday, it’s worth keeping an eye on wind and wave forecasts – even in peak season. And when you do get a perfectly calm day, you’ll appreciate it all the more, knowing it’s not a given.
Eight thousand kilometres of coastline – a Baltic Sea fact that beach-lovers will enjoy
It sounds like a textbook number, but it’s worth pausing over: the Baltic Sea coastline is about 8,000 kilometres long. That’s more than the length of the Amazon River. Along that distance stretch beaches, cliffs, river estuaries, piers, ports and wild corners that no mainstream guidebook ever mentions.
In Poland alone we have several hundred kilometres of coast, where you’ll find both sandy beaches perfect for families with children and wild stretches with dunes, forests and virtually no infrastructure. If you think you already know all the Baltic resorts – Sopot, Łeba, Międzyzdroje – try stepping off the main trail. There are still plenty of hidden spots that deserve your attention.
What makes the Baltic stand out is also the fact that its shoreline changes from year to year. Under the influence of waves, currents and storms, the sea literally redraws its outline. A place you remember from five years ago may look completely different today. And that’s exactly why it’s worth coming back.
A frozen Baltic and sledges on the ice – a winter Baltic Sea fact no one talks about
It’s not fiction or exaggeration. The Baltic really can freeze. And it has been doing so regularly for thousands of years, although today this happens less often. In the past, there were winters when ice covered entire bays and even open waters. In the 19th century and earlier, people would ride sledges over the frozen sea, organise horse-drawn rides and sometimes even use the ice as a shortcut between towns.
Today this phenomenon occurs mainly in the Gulf of Finland and the Bothnian Bay, where temperatures drop well below zero and brackish water freezes more easily. But in Poland we’ve also seen episodes of a frozen Baltic – for example in the Szczecin Lagoon or Puck Bay. Ice thickness could reach several dozen centimetres, making it safe to travel on.
It’s a fact that may sound unbelievable if you only think of the Baltic as a summer destination. But climate history shows that this sea can be harsh and icy when conditions are right.
A brackish sea that lives by its own rules – Baltic Sea facts that shape the climate
The Baltic is neither a typical sea nor a typical lake. It’s a brackish sea, combining the features of both. And it’s this unusual nature that makes its ecosystem so delicate, unstable and sensitive to change. Because of very limited water exchange with the North Sea and huge river inflows, the chemical composition of Baltic water is constantly shifting.
Every year, about 470 cubic kilometres of freshwater flow into the Baltic – mainly from the Oder, Vistula and Neva rivers. This leads to continuous stratification of the water, with layers of different salinity and temperature. In practice, this means weaker oxygenation in deeper waters and a greater risk of dead zones and faunal die-offs in some regions.
For this reason, the Baltic also has a real influence on the climate of nearby coastal regions. In summer it cools hot days, in winter it protects against extreme cold. But the balance is very fragile. That’s why this sea needs special care – not only from scientists and environmentalists, but also from everyone who spends their holidays here.
Spend your vacation with your family on the Baltic Sea!
Seals and porpoises in the Baltic – a Baltic Sea fact for nature lovers
If you think the Baltic is all about seagulls and jellyfish, it’s time to meet its more secretive residents. In these waters live grey seals and harbour porpoises, two of the most endangered marine mammals in Europe. Both species are shy, but with a bit of luck you can spot them from the shore – especially along Poland’s northern coast.
The grey seal can grow up to 2.5 metres long and weigh over 300 kg. When it’s resting on the beach, it can easily be mistaken for a log – until it moves. In recent years, their population has been increasing in places like Puck Bay and the Hel Peninsula, thanks in part to conservation efforts and the seal sanctuary in Hel.
The harbour porpoise is the only cetacean living in the Baltic. It reaches about 1.5 metres in length and rarely surfaces for more than a few seconds. It’s quiet and hard to spot, but incredibly important for local biodiversity. Unfortunately, pollution, underwater noise and fishing make its future uncertain.
The very fact that such species still live here says a lot about how unique this ecosystem really is. The Baltic may be young and relatively small, but it’s still home to creatures you won’t find anywhere else in Poland.
Enjoy a Baltic holiday in comfort at Kacze Stawy!
The Baltic isn’t just a holiday destination – it’s history, nature, weather and year-round life. And while these facts are only the beginning, the best way to get to know this sea is up close – on a beach walk, a bike trip along the coast or a quiet moment just sitting by the water.
If you’d like to see the Baltic at its most natural and beautiful, visit Holiday Park Kacze Stawy in Łeba – a place that combines proximity to the beach, comfortable accommodation and a truly family-friendly atmosphere. You’ll find everything you need here: cottages surrounded by greenery, attractions for children, bike rental, animations and, above all, an ideal starting point for discovering the Baltic’s secrets.
Check availability of our seaside cottages or rooms and plan a holiday that will genuinely surprise you – even if you think you already know the Baltic by heart.
While you’re here, make sure to visit the Słowiński National Park – it’s not just dunes, but also lakes, forests and places where you can really feel the power of nature. And if you’re curious how the Łeba dunes were formed, it’s worth knowing that their story is much longer than a few tourist seasons – it stretches back thousands of years and is still being written today.
