Has anyone seen this too?

I pulled the floor panel to do some work in a bilge tonight, just after
some rain had gone threw, just after dark. As I was surveying the
situation, I noticed a misty/smoky fog eminating from the bilge. I
looked for every explanation for it. It didn't have an obvious smell -
it definitely wasn't smoke.

I finally decided that it had to be some sort of atmospheric phenomena
- basically fog, forming from a temp. difference??

Am a crazy? or am I about to explode

Mike.