Father not going himself; coming clean on the boat; sparing Blanchett's character; Peter's body and the manifest; unchecked passport photo; missing newspaper or yearbook photo; two witnesses
Why wouldn't Dickie's dad just go to Italy and drag him back? He is too busy with his ships.
Could Ripley come clean about being Dickie on the boat with Blanchett's character? No, he would become a suspect.
Why does he kill Jack Davenport's character instead of her? Because people saw him with her, while nobody saw Davenport.
What does he do with Peter's body, presumably overboard, and how does he explain a second friend apparently killing himself when the ship's manifest is checked?
In the 1950s nobody checks anything: officials compare a passport photo of Jude Law to Matt Damon and say it checks out.
A related nit: some newspaper, or a Princeton yearbook, would surely have a real photo of Dickie Greenleaf, the famous shipping heir; the film has a lot of flaws and complicated plotting.
The Amanda Knox story is called basically a remake of this film.
This participant's middle name is Knox, which skewed their Google results for four or five years. — Amanda Dobbins
The tangent continues with a joke about not being able to go to Italy for a couple of years and being 'mostly vindicated', drawing a 'We?' reply.
Imagining being Ripley on the boat with Peter Smith Kingsley and Dickie's money, then seeing someone who knows them, would mean two witnesses; getting rid of Blanchett's character, even throwing her overboard, would at least be entertained.
Going overboard is what happens to everyone else except Freddie Miles, who gets found, while Marge gets out of it.
Peter, played by Jack Davenport, is the role to recast: an early Colin Farrell is floated though maybe too young, with a wish for a future star to make it six instead of five.
