Is there such thing as a purple lake or sea?

Yes, there are instances of lakes and bodies of water appearing purple, often due to the presence of certain microorganisms, such as purple bacteria or salt-loving algae, which can produce pigments that color the water. One notable example is Lake Hillier in Australia, which has a vibrant pink hue, but conditions can sometimes lead to a purplish appearance as well. Additionally, factors like pollution or specific mineral content can contribute to unusual water colors. However, truly purple lakes or seas are rare and typically temporary.