If you place a waterloggable block (like stairs/slabs), into a floating water source, (with 4 blocks around it), then place a block underneath it, then break the slab and block, the water will remain floating, not flowing downward.
STEPS TO RECREATE
1. Place 4 blocks in the air with a water source in the middle.
2. Place a slab or stair into the water, waterlogging the block, with the solid side facing down.
3. Place a solid block underneath the slab/stair, blocking the water.
4. Break the solid block and slab/stair you just placed.
5. The water should remain floating, not flowing downwards.
NOTE: Should any of the 4 blocks around the water break, the water will flow normally.