If everything has a purpose then evil doesn't exist

[brewer]

google 'where the Fraser river meets the ocean.' in  Vancouver BC Canada, if you want to see pictures.

You can see the fresh water on the right and salt water on the left.

Salt water and fresh water do in fact mix when agitated. These diluted salt/fresh water areas are called estuaries or brackish water zones. But this only happens when the water is agitated.

What I would actually want to see is a representative sample of pictures of river water meeting ocean war all over the world. The reason you picked the Fraser river is that is one of the very few where you can see a boundary like that. The waters are mixing fine, it's the silt that's having trouble getting through the ocean water. Temperature and density are the main factors in determing how easily river water and ocean water mix.

Isn't the idea that there's some sort of barrier between freshwater and saltwater from the Q'uran anyway? I thought you were a Christian.

Oh come on, there are no waves in the ocean to create agitation.  

Wait, I got it, god stopped all of the waves and ocean currents, just like magic.