> I am concerned with what to use for a water impervious finish of a teak
> wooden top for a bathroom vanity.
That is a figment of a fertile imagination.
There is no such thing as a good protective finish for real teak, even
Thai teak, which is protected these days.
There is a whole industry that produces "sheep dip" to protect teak in
a marine environment. None of it really works.
Ultimately, people either sell the boat, remove the teak, or let it
IMHO, a bathroom vanity top is a very poor use of good teak.
For your application, don't know what to suggest, but not teak.