This 質問 came up while I was on Tumblr: the questioned asked, Can a demon クロス the ocean because it's Salt Water?

They've never used salt water (at least i dont think so) but since it has salt in it, will it repel them または is it different?

I'm not sure. I was just wondering if they'd ever used it, because that'd answer the question. Since they haven't, it's still unknown. I've wondered similar stuff myself - like can demons swim in the sea?

Sometimes they add salt to water/holy water as a test though. I just remembered. Sam used that in S6 to prove her wasn't possessed.