The ocean looks like two separate bodies of water

It wasn’t until I viewed a video of the ocean that made me realize it looked like two separate bodies of water. A body of water floating on top of another body of water. There is a break in the middle of the horizon line, a two tone color line that –separates the two bodies of water. I can’t take a picture of it here, but if you Google a video of the ocean you’ll see what I’m talking –about. I have no idea what’s going on here, but it looks like your typical ocean water floating on top a body of black water.