This seems to be a recurring theme.  Last winter, the back leaked.
Sealing the taillights fixed the problem although we never figured out
exactly where the leak was.

Now, the driver’s side floor is filling up with a LOT of water, but
again we cannot determine the source.  There’s a gasket running along
the outside top egde of the roof, and we had racks on the car - is
that a likely source?  Or is it more likely the doors themselves?  The
seals there appear to be fine, visually.  Any hints for sleuthing this
out without having to replace all seals and gaskets?

Thanks for your help.