As much as I abhor the NK regime, it must take a lot of guts to go to sea (and submerge) in one of their submarines.

See link for details.

Rick

If the North Korean YUGO Class - so reported to have been by the western press - was lost in water deeper than 200m (656 feet) it probably experienced collapse events, either the entire pressure hull or one or more compartments depending of the sequence of events that precipitated the reported disaster.

In either of the two possibilities, a strong bubble-pulse signal detectable throughout the Sea of Japan would have been generated from which the depth of the collapsing structure could be derived.

If no bubble-pulse was produced, it can be assumed the submarine is on the bottom in water shallower than 200m and remains structurally intact.