There is no leak. If you drive through 5 feel of water, the inside of the vehicle is going to get wet. Its a Land Rover, not a submarine. As for getting rid of the smell, you need to remove the front seats, center console, rear seats, and some other trim panels to remove the complete vehicle carpet. You can try powerwashing it (top side and bottom side) in your driveway and letting it dry in the sun for a day or two. If its really bad, get it steam cleaned. Scrub the inside floorpan of the car with soap and water, then spray it all down with lysol. Put a few fans inside and let them run while the carpet is drying on its own. Unplug all electrical connectors near the floor that might have been wet (there's a lot in the kick panels), clean then with contact cleaner and apply some dielectric gel before plugging them back in. Reinstall the carpet/seats/etc and remember what a pain in the *** this all was so you don't do it again next time.
Or, just live with it and watch the mold grow. Your floors will start to rust and you will eventually get weird electrical problems from hidden connectors corroding.