Could the Gun be turned off if someone landed on the Island?

We know the Kharaa Bacterium is a water born bacteria but what if, a survivor or you landed onto the island in a pod, not touching the water and turning off the gun with no infection, thus making a new story all together. Like what if you turned it off ,and while waiting for the sunbeam, you go for a swim, don't know your infected and leave the planet thus infected the rest of Alterra space and no cure is made wiping out billions more life and the sea emperor never gets see her babies hatches and dies alone.