Because of the rule that prevent liquids from flowing on an adjacent tile with a gaz different from the one above (typically carbone dioxide in a room full of oxygen), it is possible to encounter this situation :
As you can see, there's a small amount of water, on the left, that flow ABOVE a carbone dioxide tile ! O_o
I guess there was only chlorine above the carbon dioxid, so the water push it to the left.
Steps to Reproduce
This issue has not been confirmed by a developer yet.