Sleepy Vacation Thoughts

So I was on a plane going on vacation and I woke up and looked outside the window. It looked like there was a difference in the water level. If you look closely, you can kind of see a line that separates the colour of the water.
What I thought was that maybe it would have to do with the different densities of water like the example in the "Purpose/How It Works" post.
If one level of water is denser than the other, then it would be a hard to travel across due to weight limit. We could say that the dark water is denser than the lighter body of water.

Just to be clear, I'm not exactly sure where I was and why the colour is like that because I just woke up when I saw that and I thought that it would be an example to share onto our blog. 

If you can't find the different part of ze water, look below

~Tiff and Jisu