With a rebel yell you dive head first between the lips and into the darkness beyond reasoning that fortune favours the brave!
Your foot clips the lips as you pass and they close tight, leaving you lying on your stomach in the darkess, the padded breasts of the catsuit pressing warmly against you chest. With no light at all you reach out with your latex clad hands, trying to judge your surroundings. The passage is close around you, to tight to turn around in or even sit up, but yields softly under pressure. Your hands slide off the surface easily and you can feel the occasional drip of something against your suit or even in your hair. You guess its some kind of rubber tube, widing between the wall spaces, slick to help you move through and the occasional watery noise is merely the plumbing. Its definitely not the innards of some giant you've thrown yourself into.
Definitely not. You hope.
The passage slopes slightly downwards, and after wriggling awkwardly over a lumpy section you start sliding forwards, reaching out blindly to test for obstacles in dark when something brushes against your face!