Q: My transmision won't go into reverse, or D, and it doesn´t have neutral.

There was recently a flood in my town. My tranny started failing after that. I immediately thought of water in my tran, so the next day I changed the ATF twice, which didn't solve the problem at all. The faults it shows are: I can start engine normally, when I put it in reverse, it sounds as if it's in, but it won´t move. Same thing happens when I put it in D. I tried to push the car in Neutral but the wheels are locked. The only way I can make it move is by selecting the manual mode of changing gears and selecting 2nd gear, but as soon as it downshifts to 1st gear the wheels lock, same happens when I try to shift into 3rd gear. I don't known what happens in 4th gear, I know it sounds serious, but I have one last hope of a "simple" solution before having my transmission rebuilt, which is very expensive since parts are not very available where I live. I was wondering if the problem ould have anything to do with the gear shift position sensor, which also got wet. The ATF came browish.

My car has 78000 miles.
My car has an automatic transmission.