You make a lot of good points. And I can see your version, in some respects. How about this? RW and CW are fighting. NW goes to bed, upset--annoyed. RW and CW keep arguing until CW next goes to bed. RW goes back to the stateroom/bedroom. Rouses NW, resumes fight. They alternatively wander from the stateroom to the back deck, fighting. He's jealous, drunk, provoking and accusing her. She's not quite as drunk but defensive, perhaps sarcastic or goading, tired of the control freak. She's also nervous on the boat, near the water, and is probably getting volatile. DD hears them, looks and sees her on deck in her nightgown. DD goes down and knocks. RW sends him away, goes back to the deck. DD is worried, but drunk, and used to taking orders. He doesn't want any trouble. NW tries to convince RW to come in. She is getting tired and cold but is still in the game, to some degree still incensed. Part of her is trying to get him to come in, she has anxiety about the water and the scene they are making. She puts on her jacket. DD is blaring the music. CW is either trying to tune it all out or may have passed out/gone to sleep, but he has made up his mind he is up for no more fighting ala Who's Afraid of Virginia Woolf, he's quartered for the night, maybe smokes a joint and shuts down. Maybe like me, he uses ear plugs.
Something happens and NW goes over. RW is panicky, still furious, feels (and maybe is) responsible but becomes terrified within minutes about the scandal and how he will explain all that ensued. He is in a drunken anguish but delays acknowledging what happened, to anyone, maybe even himself. Eventually, probably when necessary, he tells DD. Figures she is "gone" by now.
The Captain is smashed and weak. Depends on this for his living, is living an unexamined life, wants to get on tv, can't find the nerve to cross RW. Is able to jumble and rationalize his already fuzzy perceptions.
I still think we need a timeline.
Your theory is food for thought.
Eve