Put down stairs and put water on it. It might flow straight through it, depending on which way the water flows.
Attachments
Comments 3
@unknown This is a bug, water is not supposed to flow through the stairs / solid blocks. As you said, even Dinnerbone said that this will have to be fixed.
This is just normal water physics, not a bug. Water always flows to the lowest point, and the outside edge of the stairs has a cliff, whereas the inside has the stair blocks next to it. So outside is lower.
Dinnerbone even mentioned in the changelog: "Right now it [the water] will flow out of all faces of the block - this will change".