It's not a turn on for me to read or hear a vagina being referred to as a cavernous hole, it conjures images of something gaping and worn out, but some people are into that. It kinda goes with the term "gaping holes" in my mind, some people like it, some don't.
C.. C... Cavernous? More like sticking your hand into an sea anemone. Or into a warm pile of dough. Not a cave, though. Nothing hard about a vagina. Nothing gaping about it, either, usually. Unless you're watching some weird porn.
That's actually a giant turn off to me. I just now got into reading erotica (thanks to the bf) and right now mine is a bi book. I've thought about writing erotica, though in the past, but I would never use that phrase. Ugh, it's nasty to think about, actually.