Don’t act like I’m the only one to start thinking horrible scenarios up for people once they reveal their phobias…Oh, that is just me? *cough*

No couple inspired me, it just seemed the most logical plot for the worst nightmare of someone afraid of the ocean.
The parasailing incident was there right away. But I know some people who work on those boats and they would never let anything actually happen — bad for business. So accidents are out. Deliberately means the person doing this would know the victim intimately enough to know of the phobia. Knowing someone intimately and hating them enough to arrange murder means scorned lover.