Okay, "Dead Calm" Had Me Hooked... But What Was the DEAL??

So, I just finished watching "Dead Calm" (1989). Holy crap, that was intense! I knew basically nothing going in, just that it was some kind of thriller with Nicole Kidman (I'm on a bit of a Nicole Kidman deep dive right now, sue me). Anyway, the premise – grieving couple on a yacht meets crazy dude from a sinking ship – sounds simple, but it was SO effective. The isolation, the suspense... I was legit on the edge of my seat the whole time. Here's my theory, though. What if John (Sam Neill's character) wasn't just grieving? Like, they make it seem like the accident was purely accidental, but I kept getting this vibe that maybe he was driving that car a little reckless. Maybe he was subconsciously trying to end things too? It would explain why he's so willing to put himself in danger later, trying to 'prove' himself to Rae after she's been through so much. It would add another layer to the guilt he's clearly feeling, and kinda explain his almost suicidal bravery at the end. Thoughts? And the cinematography was amazing, particularly during the storm scenes. I almost threw up from motion sickness just WATCHING it! And Zane (Billy Zane). Dude nailed the unsettling, unpredictable vibe. He's clearly unhinged from the get-go, but the hints of charm make him way more creepy. Was he REALLY on drugs? Or just legitimately that crazy? I'm leaning towards legitimately crazy. Also, one tiny nitpick: the ending felt a tad rushed? Like, after all THAT suspense, the final confrontation felt a little too clean, considering how ruthless Zane had been up until that point. Maybe I'm just being over-critical because I was so invested. Overall, though, a super solid thriller. Definitely worth checking out if you're into suspenseful, claustrophobic movies. What do you guys think?