Placing a water bucket under a magma block or soul sand block and than replacing the water with powder snow will cause the water to disappear but it causes to make the bubble column to not get replaced. So even with leather boots you will get sunk through the powder snow whether it was a soul sand block underneath the snow or magma block. In the video I use a dispenser, but it still works by placing a powder snow in the side of a block.

https://youtu.be/zxGhZRorsLM