Hello,
I did a flight Yesterday,the Mavic mini did an error (capteur error).after it changed  direction itself, crashed on the trees and After it fallen on the water.

I will try to dry the mini.
But, in the long term,it could be have some corrosion.

How i could work the warranty for repairing.

Hi, I am sorry to know about this unfortunate incident and thank you for sharing your informative insights on what happened. I would recommend you contact our support team to start up a ticket at ( https://www.dji.com/support?site=brandsite&from=nav ). We have the professional team who would do their best to assists you with regards to this matter.Thank you.

Sensor error... I've seen that happen for strong magnetic interference.

I think you should completely disassemble the Mini and try to displace as much water as you can. A isopropyl alcohol spray or complete bath would be advisable.

People would tell you to put it in a bag of rice for couple of days and do not turn it on before you dry it.

In any event, DJI put moisture sensors on the main electronics board, if they are activated you can kiss your warranty goodbye.

Post logs to find out if it was pilot error, or drone error, only the the warranty may have you covered.
I suppose you dont have DJI Care refresh?

Thanks you for your reply.

Magnetic interférence could be possible but,there us a little bridge only..

From sunday (2 hours After the crash),the drone is on a box with bio rice...
I will be go out wednesday at the end of the day.
(3 complete  days)

I will try to post the logs as soin as possible.
I have dji Care refresh,but i would prefer tu use the normal waranty if possible.
I will do a ticket before..

You can share your log here - https://www.phantomhelp.com/LogViewer/Upload/

DJI Care Refresh is the one to go in this case. No way DJI will admit defeat, but CR will alleviate your nuisance.