I'm not sure off the top of my head whether the lines of investigation you pursue aboard ship affect the options you're given in the "unveiling" scene in Honolulu, but these tips should help you:

ABOARD SHIP

1. Investigate the scene of the crime, and take note of the blast of cold air from the ship

2. Talk to Mademoiselle Carlotta about how well she knew the victim

3. Question Jaffer on how sure he is about the time of death

Trying to avoid any outright spoilers, but when you get to Honolulu and the unveiling scene, you need to focus on the fact that the time of death is wrong, that the body was cooled rapidly by artificial means, that the ship's noise drowned out the victim's scream, and that someone aboard the vessel didn't want their business to face competition...