TIME's Pentagon correspondent Mark Thompson has been watching the investigation, and weighs in on the recent developments.
TIME.com: Is this crew member's revelation just an example of trying to make excuses for the collision?
Thompson: If he is, they're not very convincing. Plainly, if he was distracted in the middle of doing his job, that's his problem. He's not allowed to be distracted on the job.
And now it turns out the submarine sonar did, in fact, pick up the fishing boat. What do you make of that?
Thompson: I'm sort of comforted by the fact that the sub crew saw the ship about an hour before impact. So you have a track on this ship, and then you lose it. To me, it makes a lot more sense than, gee, we never saw it. At least they did see it; at least the sonar is working.
Why is the NTSB involved in what is essentially a Navy investigation?
Thompson: The NTSB was called in because this collision involved civilians and occurred in U.S. waters. And to be honest, the Navy is not at all opposed to having another set of eyes on this investigation when something like this happens out on the water and you're not in sovereign territory, issues of control can get kind of messy. Besides, if the inquiry had been totally self-contained within the Navy, it might have looked kind of suspicious.
Are the Japanese involved in this investigation at all?
Thompson: Not in any very visible way, although there will be a Japanese representative on the board of inquiry.
Will this collision lead to any new regulations for U.S. submarines operating in the Pacific?
Thompson: It's hard to say; the Japanese may press for an assurance that U.S. subs won't practice these high-speed ascents so close to shore, and the Navy may agree. But in reality, you're looking at human error here: The tools and regulations to prevent this accident were all in place, but somebody screwed up on that sub, and new regulations and rules aren't going to change that.