We’ve always heard that oil and water don’t mix, but sometimes water and water don’t mix. (Well, technically, it’s watery solutions that don’t always mix.)
When one water solution is denser than another, the less-dense water floats on top. Think about what that means. Rivers could flow through the ocean without mixing. Even during Noah’s Flood, different kinds of water could carry different kinds of fish without mixing.
You can observe this astonishing phenomenon near the coast, where the denser salt water meets freshwater. The freshwater remains distinct from the salt water, slowly mixing together at the boundary. The waters of the Amazon, for instance, can support freshwater fish for nearly 100 miles (160 km) into the Atlantic Ocean.
The same thing has been observed in ocean currents today. Colder water with more salt flows down deep for thousands of miles around the globe, while warmer, less-dense currents flow above the colder ones.
And since ocean currents can travel for many months without mixing, this might help explain how freshwater fish could survive in a world covered by salty water during the Flood. God’s design for the physics of flowing water may have been exactly what some fish needed to survive the global judgment.
We don’t usually think of water not mixing, so it’s pretty fascinating to observe. And you don’t have to travel to the Amazon or the nearest ocean; you can check it out in your own kitchen using colored sugar water.