Indonesian submarine gone amiss

[Bilge_Rat]

obviously at 800 meters, they are past crush depth.

if it is in only 3 pieces, that could indicate, the sub flooded.

If it was not flooded or partly flooded, it would implode when past crush depth and you would see hundreds of pieces, like the wreckage from the USS Thresher.

If it was flooded, then it would not implode since the water presure inside and outside the sub would equalize, but could have fractured when it hit the ocean floor since it would have been going fairly fast at that point due to gravity.

again, just speculation at this point. You are talking about a very old sub, so we have no idea what shape it was in.