Hasbee

Car drowned in the recent floods. Water level was up to the tires, but it had reached inside the boot space. Towed the car to garage, and was told that the ecu is out. Searched for nearly 3 weeks and finally found one. Had to reprogramme the immobilizer and the smart key, then the car started. After smetime had to replace the starter motor also. Now that its in running condition, however the "D" mode light is blinking. Can anyone say what would be the problem? Where to fix? Should the TCU (transmission control unit) be replaced?