you say it has happened after you backed up the car into water. even if the wheels did not go deep enought to catch the sensors, you still may have caught the trailer socket.
you should be looking for the culprit in the back of the car, you say you replaced ABS sensor in the left rear - you might have to check the right rear as well... that also may apply to the level sensors, that are on the rear axle...

also, check the battery compartment, there might be water in the battery tub...


it would help a bit, if you would include your car's model and the month/year of manufacturing, along with the mileage