I've got one of those pre-fab steam shower enclosures. Its got a
rectangular shower pan with curved corners, on top of which sits three
of those hard plastic sides. The long side has developed a "leak" of
sorts. Its not so much a leak, but I've tracked it down to when the
water droples run down that side, they wind up curving under the side
before hitting something with some brown color in it, then curving back
out into the shower. There's also a little bit of a "shelf" formed
about the rounded corner where water can collect, making things a lot
worse. I've got limited access to the interior wall behind the shower
and it does not appear that any water is leaking "out" of the shower -
merely that it is travelling from the inside to that point in between
the seams where there is some rust or something. The result of this is
that about a half houw after every shower, I have a puddle of ugly
brown liquid on the shower floor.

I have tried re-grouting the seam, but it doesn't work. It appears
there is enough water gathering at that seam that it "pushes through"
any grout I put on the interior side. I thought sealant would actually
seal things, but it doesn't appear to be a completely waterproof seal -
maybe enough to stop an occasional splash but not enough to push back
direct water contact over a 30 minute period.

I've been using normal tub and shower sealants, which are all flexible.
But in my opnion, they may be too flexible, allowing water to seap
through them. Is there any type of sealant out there that really does
form a waterproof seal in these seams. Something that is made to
withdstand more direct water contact than the typical tub and shower
sealant? Any other suggestions? I'd rather not have to rip out the
entire enclosure or anything that drastic.

Thanks in advance