random deep rectangular 'hole' appearing in my world

There are random deep rectangular 'holes' forming in my world
they are filled with water
they are deep
they form in land or water(oceans)
they all have gravel at the bottom
they destroy buildings
at first a few formed and i thought it was funny and i connected them with tunnels but it got 'serious' when one formed and destroyed my building

I have a samsung galaxy s4 mini I9190
i have v0.15.2 of minecraft pe not 1.0.0.7