However Bullying is generally considered a deliberate act intended to cause harm to the victim and when it leads to death can be viewed as premeditated. If the account of the bullying of the victim by the Captain holds up that could become a big factor here too.
A death caused during the commission of a crime can also be considered a murder even if its one of the accomplices so the marijuana and gun could also come to bear here depending on how much marijuana was actually involved.
You are confusing your disapproval with the Captain's actions (or inactions) with what the law dictates. I believe you are alluding to the possibility of the facts here sustaining a charge of felony murder. Unless there are significant unknown facts at play here, there is nothing to support that here. Just because there was a death caused during a crime doesn't make that death a "murder".
Felony murder requires facts that show an actor knowingly participated in a felony crime; once he does so, he can be found to be guilty of murder if someone dies during the commission of that felony. But only if that death was a murder
. In order for that to be the case, you need two things: an intentional participation in a felony crime, and a murder committed in the furtherance of that crime. The classic example is the multiple participant bank robbery. If two guys go into the bank and take money at gun point and one of them shoots and kills someone, then the shooter could be found guilty of murder and both the driver and the other robber could be found guilty of felony murder. You have the two elements in that example: a felony crime that all intentionally participated in (the bank robbery), and a murder that was committed in the furtherance of that felony (the intentional use of deadly force; N.B. that this would probably be Murder in the 2nd degree, not in the 1st degree. Murder 1 is generally killing someone with the intent to kill them. Murder 2 is killing someone when you didn't mean to kill them, only hurt them).
Given this framework, you can see how this just doesn't fit our facts in the sea-going case. Being mean, bullying or even cruel to someone isn't a crime. Given the prosecutor's decision to go forward with this case, you can bet that if they had more they could charge him with, they would. My supposition is that the prosecutor is as offended by the Captain's actions as you are, and he wants to see him punished. Given the clearly lower standards of culpability required under this old, archaic statute, the prosecutor probably sees this as his best chance of winning a conviction.
As I mentioned before, I was a prosecutor for about 5 years, and I am troubled by this statute. I don't think it is a good thing to be able to put someone in jail for 10 years for plain negligence. I get that captains have a greater duty of care to their crews and to their passengers; but 10 years? For plain negligence? That's too far in my book.