The Adriatic is one of the cleanest seas in Europe. There are some areas where you can see the sea bottom with a naked eye. The Adriatic is rich in 'blue' fish and it is a major source of food for the locals. However, there is much more to the Adriatic Sea. In the 19th century, doctors started prescribing sea swimming as therapy for various medical conditions. Thalassotherapy developed as a method to use seawater for cosmetic and health treatments. At the beginning of the 19th century Opatija was renowned as a Thalassotherapy resort where the Austro - Hungarian aristocracy frequent their holidays. Seawater is rich in minerals and vitamins such as magnesium, chloride, calcium, sulphate and potassium. Skin conditions such as eczema or chronic joint pains or arthritis or people who suffer from nasal congestions are well aware of swimming benefits. Swimming as an exercise is good for your heart, your lungs and it is proven to stimulate the increase of beta endorphins (the feel-good molecules) that contributes towards your mental health.