If I was building something over ice and broke a piece of ice and placed a block (not sure if this applies to all blocks or few, but it applies to a lot of them, and I know that for a fact) and I played on multiplayer, the other person would see water instead of the block that I placed. I know for a fact that it applies to Creative, I have yet to try it on Survival. The attached picture shows the one with sand (the creator of world), and the one with water (the one who joined). The pictures were taken about a second apart so it is almost same time picture. If you could fix this, it would be great.
Thanks,
CH