Well if the steward didn’t do it it’s one of the other servants. Unless of course you suspect Lady FitzSmythe of being complicit in her husband’s murder....
Actually that does sound like a fun concept a ship run like a regency estate. Rather than split the servants by gender (as irl) I’d probably have the captain as the ‘estate steward’ with the ‘steward’ and ‘technical’ teams under him (assuming the noble(s) are ‘passengers’ only). Could really get a regency drama going or branch it into an Edwardian murder mystery if your players aren’t fans of Austen.
I think it was Colonel Mustard (Imp. Marines, Ret.) in the dining room, with a candlestick.