Europe has very clean water for swimming. The European Environment Agency says this. It checked over 22,000 swimming places. 96 percent of these places meet the rules. 85 percent have a very good quality.
Austria has very clean water. Austria is in place 1 for lakes and rivers. Austria is in place 4 for the sea. Almost all 260 swimming places in Austria are great. The country spends much money on protecting the water.
Only one place in Austria is bad. It is the Pleschinger-See in Upper Austria. People should not swim there now. The reason is bacteria from water birds. All other lakes like the Lake Constance are very clean.