Everything is said in the title.

Each full block placed/destroyed, below the sea level and 10 blocks under it, causes enormous lag spikes. If I place/destroy anything else, such as stairs, walls... OR if I place/destroy a full block deep below sea level (i.e in mine shafts and underwater) the game does not lag.
It is really impossible to play and I hope the problem will be solved as soon as possible.

Block placed/destroyed makes frame rate drops to 6-10 fps instead of 90 fps while standing.
Maybe related with the issue of MC-150012.