For us Science geeks, this is really interesting!
While many of us assume Lake Michigan's water is blue because of the sky, there are actually some really cool reasons.
WGN TV says that algae, decaying organic material, sediment and dissolved organic carbon all affect it
Lake Michigan used to be greener because of the large amount of algae, BUT in the past decade, invasive mussel species have caused a massive decrease in the amount of algae by over 50%.
Not only does the water look bluer, but it now its also 20% clearer.
Its a complicated subject, but this video breaks it down well! Enjoy!