USS Connecticut (SSN 22) struck an object while submerged on Oct. 2
Former Navy submarine officer here.  This sucks, but it happens.  (It happened to a boat I was on.)It could be hitting the bottom of the ocean (which nearly killed 130+ people on the USS San Francisco years ago - https://en.wikipedia.org/wiki/USS_San_Francisco_(SSN-711)#Co...), it could be hitting another ship above it (coming to and/or operating at periscope depth is dangerous), or potentially another sub.Invariably people get fired, and whatever happens becomes a lesson learned that the Navy trains on in the future.