The Captain Dennis Davern 'alleges' that there were, aside from himself, three passengers on board at the time of Natalie Wood's mysterious and tragic death in 1981: Natalie Wood; her husband Robert Wagner; and Christopher Walken:
Natalie Wood's death to be reinvestigated by Los Angeles police | Film | guardian.co.uk
So the 3 protagonists once again:
Natalie Wood (deceased)
Robert Wagner (Her husband who, according to the spokesman for the LA Sheriff's Department is not a suspect)
Christopher Walken
What would Sherlock make of this enigmatic speculation?