If you dive in the coast of the Baltic Sea from may and for the rest of the year, this is what you will likely see: (https://www.azotelibrary.com/en/image/Omr%C

If you dive in the coast of the Baltic Sea from may and for the rest of the year, this is what you will likely see: (https://www.azotelibrary.com/en/image/Omr%C3%A5de-med-syrebrist-i-Sing%C3%B6fj%C3%A4rden%2C-%C3%96stersj%C3%B6n/Omr%C3%A5de-med-syrebrist-i-Sing%C3%B6fj%C3%A4rden%2C-%C3%96stersj%C3%B6n/14982 https://www.azotelibrary.com/en/image/Omr%C3%A5de-med-syrebr...). Similar for most lakes, except the color is then only black and brown. Miles and miles of grey, black and green mass of death.