Many people look to beat the heat of summer by heading to the water.But that same heat can make some water unhealthy... and even dangerous to humans and animals...News 12's Erick Lind tells us how high temps could lead to a boom in blue-green algae.Ethan Grindstaff and Jared Gates have grown up swimming in Crystal Lake during the summer with their friends.They've heard stories that you used to be able to see to the bottom of the lake, but it hasn't been that way since they can remember.It can also be unhealthy to swim in at certain times because of blue-green algae, but they pay attention.Ethan Grindstaff says, "The smell."Jared Gates says, "Kind of the coolness of the water. Once the water gets hot, the blue-green algae is going to come."The last few days have seen high rainfall, which can put nutrients into the water from run-off growing the algae.The Minnesota Pollution Control Agency says the smell and harmful toxin release comes when the algae dies.That can happen when the water gets warmer.It can kill pets and livestock, and children can get very ill.Minnesota Pollution Control Agency hydrologist Patrick Baskfield says, "They can range from toxins that can cause skin rashes. They can affect your respiratory system. They can raise havoc with your nervous system, circulatory system. They're just pretty tough stuff to deal with."While the weather has been warm the last couple of days, people that live in Lake Crystal and use Crystal Lake say they know when is a bad time to be in it.Grindstaff says, "Usually we just walk around and see if we can see if we can see any floating algae, and the creek is a big sign."Grindstaff says the creek leading into Crystal Lake gets really green late in the summer most years.Baskfield says last year it happened this time of year, so it is possible.Whenever it does, that's when the MPCA says you should just stay out of the water.In Lake Crystal, Erick Lind, News 12.