Obviously, he has thought about the escape route after we told him how incredibly dark and demented that was, and if I saw someone get out of my trap, if it wasn't just like a square cage, something smarter than a spikey water box, then yeah, i'd let em go.
See, you SHOULDN'T write saw, because the people in the movie apperiantly deserved that kind of punishment. If you hunted and killed jellyfish, tube worms, spotted puffer fishes, dog whelck, and crab for your own personal enjoyment and then kept them all in a spiked box full of water, yeah, that punishment would fit.