Went through high water. Transmission doesn't shift right and overdrive light blinks

Driving through Highwater could result in significant damage to various components. But it is impossible to know until you perform testing to find out what has happened. If water gets into internally lubricated items such as an engine or transmission, major problems will result. It is too soon to tell whether there is some sort of water intrusion issue. You could have electrical systems compromised due to water in wiring connectors or something on that level. Regardless, hands-on testing is required to find out what is going on here. The best news here is that your overdrive light is blinking, indicating that there are saved diagnostic trouble codes that have been set due to a failure of some kind. These codes will assist in troubleshooting what has caused the problem you are experiencing. Doesn't mean it will be easy to fix, doesn't mean it will be inexpensive. But it does mean that it will be something that you can address and find out what is wrong. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops