My cousin lives in Thailand and he moved both his car and his wifes to the nearest flyover when they knew the floods were coming. Seems that is what most people have done if they can manage without a car and the others have been preparing vehicles for wading through deep water. Fairly simple with a bike. Make sure the airbox is airtight, attach a snorkel to it and it should be OK. If the plug caps are the rubber type that seal onto the plugs they should still work (they do on a jetski after all) and it doesn't actually matter if the exhaust is under water.
