Woman turns into monster in shower

[Towhee]

So I'm about 26, and my brother (10 years older) used to watch a lot of horror flicks when we were younger. I think I was exposed to things I should have seen!  However I have this memory of a film I can't place - and it's always bothered me because of how it stuck out in my mind.

The scene (a little explicit) was a man coming home and getting into the shower. Then a woman suddenly appears, totally naked, and he is all  and they start going at it. But then she turns into this big weird monster demon thing and sucks him down the drain.

Does ANYONE know what this could be? Has to be older than like... 15 years.

[Towhee]

ER ... or maybe it wasn't a horror film at all... and just something that his younger sister REALLY SHOULD NOT HAVE BEEN WATCHING. But I clearly remember the monster. So.

[DarkenedAuras]

ehh I have no idea if this is right but a description I found said "The 1988 remake of The Blob. It wasn't even the whole movie that frightened my six-year-old brain, just the preview. A man's head is sucked through a drain pipe. That this was even a possible outcome of approaching a sink crippled me. — Anthony"

so could it possibly be the remake of The Blob?

[Andrew]

There are some matches I can think of, though none are exactly what you describe:

"Rock n Roll Nightmare" (1987)
"Creepazoids" (1987)
"Terrorvison" (1986)