You may have seen this picture a few times before:
It’s been viral a few times now and this is the explanation given with it:
I’m sorry to ruin the fun of this but that’s a lie. Actually, it’s two lies. First, the Baltic sea and the North sea are both salt water, and salt water is miscible. Being miscible has nothing to do with density. Two liquids of different densities can mix. Second, the photo wasn’t taken where it is said it was; it was taken aboard an Alaskan cruise (but I only found this out after searching).
So the moment I read that, I knew something was fishy. After a minute of Googling for “Baltic and North seas merge hoax", I found the explanation.
Here it is, in the author’s own words:
So there you go. Learn not to believe everything you are told.