It is one of the most recognisable bodies of water in Europe. Many of us visit it almost every year. What is it? It is the Baltic Sea, which in every season of the year is a delight with its colours and extremely varied coastline. This body of water is truly unique - see for yourself!

How can you describe the Baltic Sea in one sentence? Young, shallow, not too salty, not too big, but unique - that is what this sea is. The Helsinki Commission has declared 22 March as Baltic Sea Protection Day.

Least saline sea in the world

The Baltic Sea is the largest body of water brackish water in the world. It covers some 420 000 square kilometres. Why the name 'brackish sea'? The Baltic is the least saline sea in the world. On average, there are 35 grams of salt per litre of sea water. Depending on the location in the Baltic Sea, the salinity varies. It is assumed to be 7 grams per litre of water. The low salinity of the Baltic Sea has to do with the animals that live in it. It turns out that the invertebrates and fish that inhabit the Baltic Sea are up to half the size of the same species that inhabit more saline waters - such as the North Sea.

Baltic Sea in numbers

The Baltic Sea is epicontinental sea. This means that it is located on a continent and not between continents. The volume of the Baltic is about 22,000 cubic kilometres and its coastline is about 22,000 kilometres. The sea stretches for almost 1,300 kilometres from north to south. From east to west, the figure is almost half that, at around 600 kilometres.

Even more numbers!

The Baltic Sea is Europe's youngest sea. It is determined that this sea is related to the period of the last glaciation, i.e. its origin dates back 12,000 years. It is shallow sea. The average depth of the Baltic Sea is 52.3 metres. In relation to other seas, this value is really low. The average depth of the Red Sea is 490 metres and that of the Mediterranean Sea is 1438 metres. What else is worth knowing? The Baltic Sea is an exceptionally cold sea. Its average temperature ranges from 12 to 17 degrees Celsius in summer, falling as low as 0 degrees in winter.  

What colour is the Baltic Sea?

The Baltic Sea does not have a single colour. Eye-pleasing blues appear during sunny days and steel greys are noticeable during storms. However, it is not these colours that are typical of the Baltic Sea. In fact, it is one of the green seas. The waters of the Baltic are full of all kinds of suspended matter, which includes, among other things, small organisms. The green colour is also due to the low salinity of the water and its low temperature.   

Cold winters and the Baltic Sea

It is reported that the largest glaciation of the Baltic Sea took place in 1709. The thickness of the ice exceeded one metre in some places. According to sources, the sea froze so much that it was possible to walk between Denmark and Sweden. The phenomenon of the Baltic Sea freezing over is spectacular. What does the freezing of the Baltic Sea look like today? The figures will show it:

• to 15 cm of glaciation of the Kolobrzeg Coast;
• ice cover of up to 20 cm on the Gulf of Gdańsk;
• up to 25 cm of ice on the Szczecin Coast;
• up to 30 cm of ice on the Bay of Puck;
• 40 cm thick ice on the Vistula Lagoon.

The data refers to 2021. The ice cover in the Baltic Sea today lasts for two to three weeks. In the past, the phenomenon lasted - in some areas - for up to five months. 

What else can the Baltic Sea surprise us with?

The Baltic Sea is incredibly stormy. Storms and even seiches - vertical standing waves - are common in the Baltic Sea. Storm waves are quite steep and short. The average wave in the Baltic Sea is 5 metres high during a storm. When the storm is exceptionally strong, the average wave doubles in height - which means it can reach heights of up to 10 metres.

Summary of knowledge about the Baltic Sea

What should you remember about the body of water you are likely to swim in? Here's knowledge in a nutshell that you can surprise your friends with over lunch at a fish fry. Baltic Sea it:

• brackish water reservoir;
• epicontinental sea;
• shallow sea;
• the youngest sea in Europe;
• low water temperatures.