If you right-click on a slab, stair, fence post etc. then nothing will happen. The only way to get something to be waterlogged is running the command setblock X Y Z minecraft:oak_fence[waterlogged=true] (I know it's not just oak fences; I was making an example.)
MC-130192
Slabs, fence posts and things like that cannot be waterlogged
Resolved
Cannot Reproduce
0
Cannot confirm. Right clicking a slab, stair, or fence post with a water bucket makes the block waterlogged.