Hell in the first book, Jonas drove one of those fast little subs they have right down the sharks throat, then got out, used one of the sharks teeth to saw a hole in the stomach, then crawled throught the sharks body to the heart and used the tooth to sever all the arteries connected to the heart. He then managed to crawl back through the body, back through the hole in the stomach, back into the mini sub and managed to pilot it back to the surface.
That's how I remember it anyway, I read that book over 20 years ago.