If you take someone that's observably drunk/impaired in a certain situation and make it possible for them to get into a different situation you'd very likely expose yourself to liability.
As in, you pull a drunk boater out of the mud or off a sandbar. They then proceed to cause damage or harm others, a feat they wouldn't have been able to accomplish had you not gotten them loose.
Oh, I'm with the sane people out there that wouldn't begin to think there's any chance of a good samaritan deed like this turning into a bigger disaster.
Let alone being held culpable as part of it.
But make no mistake, in the event of something unfolding like that you'd be foolish to bet against an injured party's lawyer looking to find as many defendants as possible should lawsuits develop. For this I'm glad to maintain additional umbrella policy coverage.
I don't want to rain on anyone's fun, but if I were in a situation involving rendering aid to someone that clearly showed signs of being unable to lawfully operate the vessel and they insisted on doing so after my assistance I'd absolutely reach out to the authorities for help. I'd like to think clearer heads would prevail and they'd accept the suggestion of it being a better idea to "anchor over there and sleep it off."
But then I generally prefer to avoid boating in situations where I'm ever going to encounter that sort of nonsense, so it's really not a factor for me. What's the saying about God favoring drunks and idiots? I'd rather not get in-between that.