After a night out drowning her sorrows, a lonely woman wakes up next to a man she just met and discovers they are on his boat in the middle of the ocean and it’s sinking fast.

I can't envision a thriller based on trying to keep sinking boat afloat. Think titanic. That was actually a love story. If you are still developing this idea how about something like this:

?After a night of indiscretion, a woman wakes up on a boat next to a strange man and that's not her only problem. The stranger seems intent on killing her. ?

Still you have the problem of a whole movie taking place on a boat so not many places to run! Would need to move action aground.

What's the story about?? Figuring out how and why she got into the predicament?? Or figuring a way out of her predicament?

What's the story about?? Figuring out how and why she got into the predicament?? Or figuring a way out of her predicament?