Hollow Man: Second Blood,

When Linda McKay and josh brolin released the elevator shaft, sending Sebastian Caine plunging into a raging inferno, they thought the nightmare was over. They were wrong.
The initial explosion triggered a secondary gas blast, creating a massive downward shockwave that threw Sebastian sideways through a collapsed wall into the facility's high-pressure sub-basement cooling pipes. Hitting icy, rushing water instead of concrete, the sudden thermal shock saved his life. The rapid current swept his unseen, badly burned body through the underground drainage network, flushing him out.
Exiting thriller fictional.