I was messing around with my world and trying to drop a block of concrete powder above the flowing water. Right when the concrete powder touches the water, it stop falling and just floats, while sand and gravel falls down just fine.

To reproduce this bug:

-Grab a block of concrete powder, a water bucket and any blocks.

-Build a pillar at any height.

-Put water anywhere on the pillar.

-Drop a block of concrete powder above the water scrouce.