Hi, Michael. Once you have water in the tank, you have very few options. If you cannot siphon the water off the bottom…which is all but impossible in modern vehicles these days, your options are limited. Assuming you don’t have gross water contamination and you have a way of angling the vehicle such that the water pools up away from the fuel pick up, then you could run out essentially all the gas. Then you can add “Anhydrous Isopropyl Alcohol” or “Anhydrous n-Propanol,” one of which should be available at a paint store. Do not use anything less than 99% active. The alcohol will absorb the water and carry it into the gasoline. I’d put as much as a gallon of alcohol and then fill up on top of that with fresh gas. Best of luck!